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    1. Verbal Fluency TestGradeA
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    16,361Registered studies name a cognitive test in an outcome measure11,688 name a test you can run hereExplore the studies
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  1. Home
  2. /Data
  3. /Clinical trials
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  5. /Cognitive impairment and decline

Clinical trials data

Cognitive tests in cognitive impairment and decline trials: 354 registered studies

Every registered cognitive impairment and decline study on ClinicalTrials.gov that names a cognitive test in an outcome measure: the tests used most, how often as a primary outcome, which tests go together, how large the studies are and when they measure the outcome.

Registered cognitive impairment and decline studies name a cognitive test in an outcome
354
Name one in a primary outcome
230
See the tests
Median participants per study
75
By phase
Led by industry
32

The tests cognitive impairment and decline trials use most

Verbal Learning leads: 79 of the 354 studies name it, 22%. Next comes the Trail Making Test (77). As a primary outcome, Verbal Learning leads with 43 studies.

  1. 1

    Verbal Learning79 studies, 43 as a primary outcome

  2. 2

    Trail Making Test77 studies, 33 as a primary outcome

  3. 3

    Verbal Fluency63 studies, 35 as a primary outcome

  4. 4

    Digit Span Test60 studies, 29 as a primary outcome

  5. 5

    Stroop Color-Word Test47 studies, 24 as a primary outcome

  6. 6

    Symbol Coding40 studies, 18 as a primary outcome

  7. 7

    Picture Naming Test23 studies, 15 as a primary outcome

  8. 8

    Category Fluency22 studies, 11 as a primary outcome

  9. 9

    Clock Drawing Task21 studies, 10 as a primary outcome

  10. 10

    N-Back Task16 studies, 10 as a primary outcome

  11. 11

    Complex Figure Copy and Recall14 studies, 7 as a primary outcome

  12. 12

    Continuous Performance Test14 studies, 6 as a primary outcome

  13. 13

    Size Order Memory Test13 studies, 5 as a primary outcome

  14. 14

    Short Story Recall10 studies, 6 as a primary outcome

  15. 15

    Picture Order Memory Test10 studies, 4 as a primary outcome

  16. 16

    Letter-Number Sequencing Task9 studies, 8 as a primary outcome

  17. 17

    Selective Reminding Task9 studies, 6 as a primary outcome

  18. 18

    Dimensional Change Card Sort9 studies, 4 as a primary outcome

  19. 19

    Pattern and Letter Comparison9 studies, 4 as a primary outcome

  20. 20

    Card Sorting Test (Berg)8 studies, 5 as a primary outcome

  21. 21

    Matrix Reasoning8 studies, 4 as a primary outcome

  22. 22

    Paired Associate Learning7 studies, 5 as a primary outcome

  23. 23

    Task Switching Test7 studies, 4 as a primary outcome

  24. 24

    Go/No-Go Task7 studies, 2 as a primary outcome

  25. 25

    Rapid Visual Information Processing6 studies, 5 as a primary outcome

A test as a primary outcomeOnly in secondary or other outcomes

26% of cognitive impairment and decline studies name only instruments outside the library, such as clinician-administered screening scales. They count in every figure on this page and are not listed. The explorer below holds all 82 tests.

Tests used together

The pairs of tests cognitive impairment and decline studies name together most often.
  1. Trail Making Test and Verbal Learning34 studies name both
  2. Trail Making Test and Verbal Fluency29 studies name both
  3. Digit Span Test and Verbal Learning27 studies name both
  4. Stroop Color-Word Test and Trail Making Test26 studies name both
  5. Digit Span Test and Trail Making Test25 studies name both
  6. Verbal Fluency and Verbal Learning24 studies name both
  7. Stroop Color-Word Test and Verbal Learning20 studies name both
  8. Symbol Coding and Verbal Learning19 studies name both
  9. Digit Span Test and Verbal Fluency17 studies name both
  10. Category Fluency and Verbal Learning16 studies name both

Studies by start year

Each study counted once. 2026 is partly planned starts.
02000: 0 studies, 0 with a test as a primary outcome20002001: 0 studies, 0 with a test as a primary outcome2002: 1 studies, 1 with a test as a primary outcome2003: 0 studies, 0 with a test as a primary outcome2004: 0 studies, 0 with a test as a primary outcome2005: 1 studies, 0 with a test as a primary outcome20052006: 0 studies, 0 with a test as a primary outcome2007: 2 studies, 1 with a test as a primary outcome2008: 2 studies, 2 with a test as a primary outcome2009: 2 studies, 2 with a test as a primary outcome2010: 5 studies, 4 with a test as a primary outcome20102011: 4 studies, 1 with a test as a primary outcome2012: 8 studies, 7 with a test as a primary outcome2013: 8 studies, 7 with a test as a primary outcome2014: 8 studies, 5 with a test as a primary outcome2015: 11 studies, 7 with a test as a primary outcome20152016: 16 studies, 10 with a test as a primary outcome2017: 34 studies, 18 with a test as a primary outcome2018: 20 studies, 14 with a test as a primary outcome2019: 36 studies, 22 with a test as a primary outcome2020: 21 studies, 14 with a test as a primary outcome20202021: 23 studies, 16 with a test as a primary outcome2022: 25 studies, 15 with a test as a primary outcome2023: 36 studies, 22 with a test as a primary outcome2024: 32 studies, 24 with a test as a primary outcome2025: 31 studies, 19 with a test as a primary outcome20252026: 26 studies, 17 with a test as a primary outcome

A test as a primary outcomeOnly in secondary or other outcomes

Show as a table
Registered studies by start year
Start yearStudiesA test as a primary outcome
200000
200100
200211
200300
200400
200510
200600
200721
200822
200922
201054
201141
201287
201387
201485
2015117
20161610
20173418
20182014
20193622
20202114
20212316
20222515
20233622
20243224
20253119
20262617

Phases and sponsors

By phase

  • Early phase 16 studies, 6 as a primary outcome
  • Phase 16 studies, 3 as a primary outcome
  • Phase 1/28 studies, 7 as a primary outcome
  • Phase 217 studies, 9 as a primary outcome
  • Phase 2/33 studies, 2 as a primary outcome
  • Phase 36 studies, 5 as a primary outcome
  • Phase 419 studies, 12 as a primary outcome
  • Not applicable217 studies, 146 as a primary outcome
  • Observational72 studies, 40 as a primary outcome

Sponsors and study types

Lead sponsor: industry 32, NIH 0, universities, hospitals and others 322. Interventional 282, observational 72.

Status, results, interventions and countries

Status

  • Recruiting57 studies, 38 as a primary outcome
  • Not yet recruiting18 studies, 12 as a primary outcome
  • Active, not recruiting17 studies, 14 as a primary outcome
  • Completed152 studies, 96 as a primary outcome
  • Stopped early22 studies, 12 as a primary outcome
  • Status unknown88 studies, 58 as a primary outcome

What they test

  • Behavioral72 studies, 46 as a primary outcome
  • Drug67 studies, 45 as a primary outcome
  • Device44 studies, 33 as a primary outcome
  • Dietary supplement43 studies, 32 as a primary outcome
  • Procedure12 studies, 9 as a primary outcome
  • Diagnostic test17 studies, 7 as a primary outcome
  • Biological6 studies, 2 as a primary outcome
  • Radiation3 studies, 2 as a primary outcome
  • Combination product1 studies, 1 as a primary outcome
  • Other102 studies, 61 as a primary outcome
  • None given24 studies, 14 as a primary outcome

Intervention types as registered. A study can list several; observational studies often list none.

Where their sites are

  • United States91 studies, 62 as a primary outcome
  • China43 studies, 32 as a primary outcome
  • Canada20 studies, 13 as a primary outcome
  • France20 studies, 7 as a primary outcome
  • Spain19 studies, 14 as a primary outcome
  • Italy16 studies, 12 as a primary outcome
  • Taiwan14 studies, 5 as a primary outcome
  • United Kingdom13 studies, 6 as a primary outcome
  • Egypt10 studies, 8 as a primary outcome
  • South Korea10 studies, 7 as a primary outcome
  • Germany7 studies, 2 as a primary outcome
  • Israel7 studies, 6 as a primary outcome

43 countries in all. A study with sites in several counts in each; 22 list no site.

Reported results

Completed studies with results posted on ClinicalTrials.gov, a results paper the registry links to the study, or both.

Completed cognitive impairment and decline studies: 68 of 152, 45%

Every completed study with a cognitive outcome: 3,626 of 7,953, 46%

Completed cognitive impairment and decline studies and every completed study, by how they reported results
ResultsCompleted cognitive impairment and decline studiesEvery completed study
Results on ClinicalTrials.gov and a paper12, 8%776, 10%
Results on ClinicalTrials.gov only31, 20%1,139, 14%
A results paper only25, 16%1,711, 22%
Neither84, 55%4,327, 54%

How many participants they enroll

Enrollment as registered: actual for a finished study, planned for one still recruiting.
102050100200
  • Phase 240 median, 14 to 65
  • Phase 480 median, 48 to 102
  • Not applicable60 median, 35 to 126
  • Observational122 median, 63 to 243
Participants per study. The bar spans the middle half of the studies in each phase, the mark is the median, and the axis is logarithmic. Phases with fewer than 10 studies that give a size are left out.
Show as a table
Participants per cognitive impairment and decline study by phase
PhaseStudies with a sizeMedianMiddle half
Phase 2154014 to 65
Phase 4198048 to 102
Not applicable2146035 to 126
Observational7212263 to 243

When the cognitive outcome is measured

Half of the primary outcomes that name a library test are measured within 13 weeks of the start, and the middle half from 4 weeks to 11 months. 348 primary outcomes give a duration.

Latest time point of each outcome

  • Within a day120 outcomes, 58 as a primary outcome
  • Up to 4 weeks59 outcomes, 38 as a primary outcome
  • 1 to 3 months162 outcomes, 108 as a primary outcome
  • 3 to 6 months143 outcomes, 51 as a primary outcome
  • 6 to 12 months92 outcomes, 37 as a primary outcome
  • 1 to 2 years70 outcomes, 46 as a primary outcome
  • Over 2 years27 outcomes, 10 as a primary outcome
  • No duration given30 outcomes, 16 as a primary outcome

A test as a primary outcomeOnly in secondary or other outcomes

673 of the 703 outcome measures give a duration. A single visit counts as within a day.

Median time to the primary outcome, by test

Median weeks to the latest time point of each test's primary outcomes
TestPrimary outcomesMedian
Verbal Learning4113 weeks
Verbal Fluency3413 weeks
Trail Making Test3213 weeks
Digit Span Test2812 weeks
Stroop Color-Word Test2312 weeks
Symbol Coding1713 weeks
Picture Naming Test156 months
Category Fluency116 months
N-Back Task102 weeks

Explore the cognitive impairment and decline studies

The 262 cognitive impairment and decline studies that name a test in the library, with filters for test, phase, sponsor, status, country, intervention, outcome list, size and start year. Each study links to its record on ClinicalTrials.gov.
ConditionCognitive impairment and decline

262 studies match. 162 name a library test in a primary outcome. Median size 65 participants. Median time to the primary outcome: 13 weeks.

Loading 262 studies; the filters turn on when they arrive.

By start year
01020302000: 0 studies, 0 naming a library test in a primary outcome20002001: 0 studies, 0 naming a library test in a primary outcome2002: 1 studies, 1 naming a library test in a primary outcome2003: 0 studies, 0 naming a library test in a primary outcome2004: 0 studies, 0 naming a library test in a primary outcome2005: 1 studies, 0 naming a library test in a primary outcome20052006: 0 studies, 0 naming a library test in a primary outcome2007: 2 studies, 1 naming a library test in a primary outcome2008: 2 studies, 2 naming a library test in a primary outcome2009: 2 studies, 2 naming a library test in a primary outcome2010: 4 studies, 3 naming a library test in a primary outcome20102011: 4 studies, 1 naming a library test in a primary outcome2012: 7 studies, 6 naming a library test in a primary outcome2013: 8 studies, 7 naming a library test in a primary outcome2014: 8 studies, 4 naming a library test in a primary outcome2015: 10 studies, 7 naming a library test in a primary outcome20152016: 13 studies, 9 naming a library test in a primary outcome2017: 23 studies, 11 naming a library test in a primary outcome2018: 17 studies, 11 naming a library test in a primary outcome2019: 22 studies, 12 naming a library test in a primary outcome2020: 12 studies, 7 naming a library test in a primary outcome20202021: 17 studies, 11 naming a library test in a primary outcome2022: 19 studies, 12 naming a library test in a primary outcome2023: 27 studies, 17 naming a library test in a primary outcome2024: 21 studies, 15 naming a library test in a primary outcome2025: 24 studies, 12 naming a library test in a primary outcome20252026: 16 studies, 9 naming a library test in a primary outcome

2026 is partly planned starts. Not shown: 1 planned to start after 2026 and 1 with no start year.

Show as a table
Matching studies by start year
Start yearStudiesAs a primary outcome
200000
200100
200211
200300
200400
200510
200600
200721
200822
200922
201043
201141
201276
201387
201484
2015107
2016139
20172311
20181711
20192212
2020127
20211711
20221912
20232717
20242115
20252412
2026169

Library tests named most

Conditions

  • Cognitive impairment and decline262 studies, 162 as a primary outcome

Phases

Participants

Lead sponsor: industry 24, other 238. Interventional 219, observational 43.

As a primary outcomeSecondary or other outcome

The studies, newest registration first

Each number opens the study's record on ClinicalTrials.gov.

Registered studies that match the filters, newest registration first, with the library tests each one names and the outcome list that names them.
StudyStartPhaseConditionsParticipantsLead sponsorStatusLibrary tests named, with the latest time point
NCT07895979Start2026PhaseNot applicableConditionsCognitive impairment and declineParticipants216Lead sponsorOtherStatusRecruitingLibrary tests named
  • Tower of HanoiSecondary12 weeks
NCT07891650Start2026PhaseNot applicableConditionsCognitive impairment and declineParticipants160Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Trail Making TestSecondary6 months
  • Verbal LearningSecondary6 months
  • Digit Span TestSecondary6 months
NCT07872189Start2027PhaseNot applicableConditionsCognitive impairment and declineParticipants136Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Verbal FluencyPrimary6 months
NCT07833644Start2023PhaseNot applicableConditionsCognitive impairment and declineParticipants36Lead sponsorOtherStatusActive, not recruitingLibrary tests named
  • Trail Making TestPrimary8 weeks
  • Verbal LearningPrimary8 weeks
  • Clock Drawing TaskPrimary8 weeks
NCT07802392Start2026PhaseNot applicableConditionsCognitive impairment and declineParticipants230Lead sponsorOtherStatusRecruitingLibrary tests named
  • Verbal FluencyPrimary1 week
  • Digit Span TestPrimary1 week
NCT07766642Start2026PhaseNot applicableConditionsCognitive impairment and declineParticipants35Lead sponsorIndustryStatusActive, not recruitingLibrary tests named
  • Digit Span TestPrimary8 weeks
NCT07753382Start2026PhaseNot applicableConditionsCognitive impairment and declineParticipants36Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Trail Making TestSecondary6 months
  • Stroop Color-Word TestSecondary6 months
  • Picture Naming TestSecondary6 months
  • Clock Drawing TaskSecondary6 months
NCT07751510Start2026PhaseNot applicableConditionsCognitive impairment and declineParticipants75Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Stroop Color-Word TestSecondary13 weeks
  • Verbal LearningPrimary13 weeks
  • Verbal FluencyPrimary13 weeks
  • Digit Span TestSecondary13 weeks
  • Symbol CodingSecondary13 weeks
NCT07668440Start2026PhaseNot applicableConditionsCognitive impairment and declineParticipants71Lead sponsorOtherStatusActive, not recruitingLibrary tests named
  • Verbal FluencyPrimary13 weeks
  • Symbol CodingPrimary13 weeks
  • Category FluencyPrimary13 weeks
NCT07584408Start2019PhaseNot applicableConditionsCognitive impairment and declineParticipants15Lead sponsorOtherStatusStopped earlyLibrary tests named
  • Trail Making TestPrimary4 weeks
NCT07564804Start2025PhaseNot applicableConditionsCognitive impairment and declineParticipants60Lead sponsorIndustryStatusCompletedLibrary tests named
  • Digit Span TestPrimary8 weeks
NCT07547319Start2026PhaseNot applicableConditionsCognitive impairment and declineParticipants80Lead sponsorOtherStatusRecruitingLibrary tests named
  • Triplet Odd-One-Out TaskSecondary3 weeks
NCT07531888Start2026PhaseNot applicableConditionsCognitive impairment and declineParticipants20Lead sponsorOtherStatusRecruitingLibrary tests named
  • Verbal LearningPrimary6 weeks
  • Verbal FluencyPrimary6 weeks
  • Digit Span TestPrimary6 weeks
  • Tower PlanningPrimary6 weeks
  • Corsi Block-Tapping TestPrimary6 weeks
NCT07463391Start2026PhaseNot applicableConditionsCognitive impairment and declineParticipants60Lead sponsorOtherStatusRecruitingLibrary tests named
  • Stroop Color-Word TestSecondary6 months
  • Verbal LearningSecondary6 months
  • Digit Span TestSecondary6 months
  • Picture Naming TestSecondary6 months
NCT07453537Start2026PhaseNot applicableConditionsCognitive impairment and declineParticipants84Lead sponsorOtherStatusRecruitingLibrary tests named
  • Verbal LearningSecondary2 years
  • Vocabulary TestSecondary2 years
  • Size Order Memory TestSecondary2 years
  • Pattern and Letter ComparisonSecondary2 years
  • Picture Order Memory TestSecondary2 years
  • Arithmetic Fluency TaskPrimary2 years
NCT07448675Start2023PhaseObservationalConditionsCognitive impairment and declineParticipants230Lead sponsorOtherStatusRecruitingLibrary tests named
  • Oddball Target DetectionSecondary12 weeks
  • Antisaccade TaskSecondary12 weeks
NCT07412977Start2026PhaseObservationalConditionsCognitive impairment and declineParticipants5,160Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Generation Effect TaskWording unclear
NCT07402161Start2025PhaseObservationalConditionsCognitive impairment and declineParticipants250Lead sponsorOtherStatusRecruitingLibrary tests named
  • Trail Making TestSecondary2 years
  • Verbal LearningSecondary2 years
  • Verbal FluencySecondary2 years
  • Category FluencySecondary2 years
  • Short Story RecallSecondary2 years
  • Complex Figure Copy and RecallSecondary2 years
NCT07377500Start2026PhaseNot applicableConditionsCognitive impairment and declineParticipants356Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Letter-Number Sequencing TaskPrimary12 months
NCT07342075Start2025PhaseObservationalConditionsCognitive impairment and declineParticipants50Lead sponsorOtherStatusRecruitingLibrary tests named
  • Trail Making TestSecondary6 months
NCT07334912Start2025PhasePhase 2ConditionsCognitive impairment and declineParticipants188Lead sponsorIndustryStatusRecruitingLibrary tests named
  • Dimensional Change Card SortSecondary6 months
  • Size Order Memory TestSecondary6 months
  • Picture Order Memory TestSecondary6 months
NCT07334366Start2025PhaseNot applicableConditionsCognitive impairment and declineParticipants100Lead sponsorOtherStatusRecruitingLibrary tests named
  • Verbal LearningPrimary12 weeks
  • Digit Span TestPrimary12 weeks
  • Continuous Performance TestPrimary12 weeks
NCT07272174Start2026PhaseNot applicableConditionsCognitive impairment and declineParticipants50Lead sponsorOtherStatusRecruitingLibrary tests named
  • Verbal LearningPrimary6 months
  • Eriksen Flanker TaskSecondary6 months
  • Dimensional Change Card SortSecondary6 months
  • Size Order Memory TestSecondary6 months
  • Pattern and Letter ComparisonSecondary6 months
  • Picture Order Memory TestSecondary6 months
NCT07242495Start2024PhaseNot applicableConditionsCognitive impairment and declineParticipants34Lead sponsorOtherStatusRecruitingLibrary tests named
  • Trail Making TestPrimary6 weeks
NCT07198399Start2025PhaseNot applicableConditionsCognitive impairment and declineParticipants35Lead sponsorIndustryStatusCompletedLibrary tests named
  • Digit Span TestPrimary8 weeks

Page 1 of 11

Questions, answered from the data

Which cognitive test do cognitive impairment and decline trials use most?

Verbal Learning: 79 of the 354 registered studies name it in an outcome measure, 22%. Next come the Trail Making Test (77) and Verbal Fluency (63).

Which cognitive test do cognitive impairment and decline trials use most as a primary outcome?

Verbal Learning, named in a primary outcome by 43 studies. 230 of the 354 studies, 65%, name a cognitive test in a primary outcome.

How many participants does a phase 2 cognitive impairment and decline trial enroll?

Half of the phase 2 cognitive impairment and decline studies enroll 40 participants or fewer, and the middle half enroll 14 to 65. 15 of them give a size.

How long after the start do cognitive impairment and decline trials measure a cognitive outcome?

Half of the primary outcomes that name a library test are measured within 13 weeks of the start, and the middle half from 4 weeks to 11 months. 348 primary outcomes give a duration.

Which cognitive tests do cognitive impairment and decline trials use together?

The Trail Making Test with Verbal Learning most often: 34 studies name both. Next, the Trail Making Test with Verbal Fluency (29).

How many completed cognitive impairment and decline trials have reported results?

68 of the 152 completed cognitive impairment and decline studies, 45%, have reported results: 43 posted them on ClinicalTrials.gov, 37 have a results paper linked to the registry record, and 12 did both. The other 84 show neither. Of all completed studies with a cognitive outcome, 46% have reported results.

Other conditions

  • Dementia and Alzheimer's1,673 studies
  • Aging, frailty and exercise1,398 studies
  • Depression and bipolar disorder1,247 studies
  • Stroke1,233 studies
  • Substance use and addiction895 studies
  • Parkinson's disease892 studies
  • Mild cognitive impairment859 studies
  • Cancer760 studies
  • Sleep and sleep disorders749 studies
  • Anxiety, PTSD and OCD692 studies
  • Cardiovascular disease682 studies
  • Pain and fatigue681 studies
  • Healthy volunteers656 studies
  • Schizophrenia and psychosis640 studies
  • Obesity and diabetes627 studies
  • Delirium, surgery and intensive care619 studies
  • Multiple sclerosis612 studies
  • Brain injury and concussion444 studies
  • ADHD357 studies
  • Hearing loss247 studies
  • COVID-19 and long COVID221 studies
  • Autism200 studies
  • Epilepsy138 studies
  • Lung disease110 studies

All 16,361 registered studies, by test, condition, phase and year.

How the studies are counted

For each test family, the census runs ClinicalTrials.gov's own outcome search for the family's names and reads every study first posted by the day the family was counted. These studies were read on 10 November 2026. A study counts once on a page, however many tests it names. Counts for a test cover every version of the task under any of its names, so a page can count studies that used a commercial version.

The census adds two things to each record and changes nothing in it: which outcome list names the test (primary, then secondary, then other), and the condition groups, matched on the study's condition names and MeSH terms. A study can fall in several groups; one whose only condition is cognitive impairment or decline falls in “Cognitive impairment and decline”. Studies that name only instruments outside the library count in every total and share but are not listed.

A second read on 10 November 2026 added each study's overall status, whether results are posted, its intervention types, the countries of its sites and the time frame of the outcome that names each test. A time frame counts by the latest time point it names: “Baseline, 12 and 24 weeks” is 24 weeks, a single visit is within a day, and one that names no duration, such as “end of treatment”, is left out of the timings.

A third read on 10 November 2026 added the papers the registry links to each study: those its sponsor lists as reporting results, and those PubMed links to it through the study's NCT number. A study has a results paper when one of them came out in or after the month of its primary completion and PubMed does not class it as a protocol, review or comment. A paper that never gives the NCT number is not linked, so some studies counted as reporting neither did publish.

Source: ClinicalTrials.gov, a database of the U.S. National Library of Medicine, which does not endorse these pages. Every study line is in the data release 2.1.0, and the explorer's own file is clinical-trials-studies.json.

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