Publishers can include:
University Presses, such as the University of Georgia. The information is typically scholarly in nature.
Commercial Publishers and those associated with scholarly societies also publish reliable scholarly materials. Examples are the Modern Language Association or the American Psychological Association.
Vanity Presses are publishers who are paid by the author to publish the material. Be cautious with this type of material.
This information is taken from the ONLINE LIBRARY LEARNING CENTERTutorial from GALILEO. Additional information on evaluating sources is linked here.
Additional information on university presses can be found in the following article from the American Association of University Presses.