Notes Here are some useful tips for using Medline. To change years or search other OVID databases, searches can be re-run by clicking on the Change Database key and choosing yes when asked if you would like to re-run the search. Click on a Subject Heading to view its tree - related terms that are more general and more specific. Select the Explode box if you wish to retrieve citations using the selected term and all of its more specific terms. Select the Focus box if you wish to limit your search to those documents in which your subject heading is considered the major point of the article. If your search did not map to a subject heading, select the box Search as Keyword. Subheadings can be used to restrict the focus of your search. Select one or more subheadings by clicking in the box that precedes each desired subheading. Choose Combine with AND to search for the intersection of two or more subheadings. Choose Combine with OR to search for the union of two or more subheadings. If you do not wish to restrict the focus of your search, then select Include All Subheadings. Click the Subheading button to get more information about the scope of the subheading.