(Ruth Szpunar at DePauw University)
The best sources to cite are scholarly, scientific journal articles that are "peer-reviewed" (screened for publication by the author's peers).
Primary Article - First report of new research that includes actual data and describes experimental methods
Review Article - Secondary report that summarizes and discusses previous research findings
The databases below can help you to locate scholarly, scientific, and/or peer-reviewed articles relevant to the biological sciences.
Some sources can be consulted for ideas or background, but cannot take the place of peer-reviewed journals. For example:
Websites - Avoid citing personal websites (even those of scientists) unless they are hosted by a scientific research institution.
Encyclopedias - Avoid citing encyclopedias unless they are science-specific and peer-reviewed, e.g. Encyclopedia of Life Sciences (eLS).
Magazines - Avoid citing general magazines (even science magazines like Discover or Science News).
Books - Avoid citing books unless they are written by and for scientists, and published by a scientific or university press. Books are usually secondary sources.