Table 1. Reasons for citations in the methods section.
| Category | Example | Potential shortcut |
|---|---|---|
| How (Explain a method): The citation was intended to explain how something was done. This category included 4 subcategories for specific types of citations (1. General, 2. Protocol, 3. Prior publication describing the study design and/or results, and 4. Guideline or manual). | Liver samples were collected, sectioned, and frozen as described previously (citation). | Yes |
| Who or what (Give credit or specify what was used): The citation is used to give credit to the group that created the method, tool, resource or substance, or to specify exactly what method, tool, resource, or substance was used. The citation is not used to explain how the method was performed, or how the tool, resource or substance was used. This category includes 3 subcategories (1. Software, 2. Atlas, 3. Other). | Analyses were conducted using R (citation of R). | No |
| From where (Source of materials): The citation is used to show where a substance or organism was obtained from, not how the substance or organism was created. | Mice were obtained from the Smith lab (citation). | No |
| Why (Provide context or a justification): The citation refers to previous studies to provide context. This includes citations that compare the authors’ results with results from previous studies, demonstrate that others have used a similar approach, or explain why the authors chose a particular method, model, formula, etc. The citation is not intended to provide insight into how the existing study was conducted. | In accordance with previous studies (citation), we observed that the optimal treatment dose was 20 ml. | No |
| Formula or value: The citation referred to a formula or specified a value for a parameter that was used. The formula or value had to be stated in the article, so that the reader would not need to look up this information in the cited resource. The citation was not used to explain how that parameter was calculated, how the formula was derived, or why the parameter or formula was chosen. | Drug cost $X for drug Y was obtained from publicly available reports (citation). | No |
| Other: Citations that do not fit into the other categories. | Yes |
A complete protocol with examples is available in the online repository.