| 削除: NCCIH: How To Make Sense of a Scientific Journal Article - Types of Research | https://www.nccih.nih.gov/health/know-science/how-to-make-sense-of-a-scientific-journal-article/methods/types-of-research |
| 追加: NCI Dictionary: Observational Study | https://www.cancer.gov/publications/dictionaries/cancer-terms/def/observational-study |
| 削除: ClinicalTrials.gov: Glossary | https://clinicaltrials.gov/study-basics/glossary |
| 追加: NCI: Observational Studies | https://www.cancer.gov/research/participate/how/observational-studies |
