Wikipedia articles should be based on reliable, published sources, making sure that all majority and significant minority views that have appeared in those sources are covered. If no reliable sources can be found on a topic, Wikipedia should not have an article on it. See Wikipedia:Reliable Sources for more information.
While the use of open access resources is encouraged (information not behind logins and paywalls), information obtained through databases and similar sources can be used in Wikipedia, such as through Rowan's databases, because they are from reliable, published sources.
An important technique for evaluating sources, especially those online, is lateral reading, which involves comparing sources. See Evaluating Online Sources: A Toolkit for more information.
Sources must be verifiable, meaning that people are able to check that information comes from a reliable source, or previously published information rather than editors' beliefs, experiences, or previously unpublished ideas or information.
See Wikipedia:Verifiability for more information.