Remember that no one expects you to be an expert in everything. You are, therefore, expected to give credit where credit is due. Citing sources makes you look more knowledgeable and professional. When in doubt, cite it.

If you have just a partial citation (like an author, date, and subject) use Google Scholar to piece together the missing information.

You can often find theses and dissertations in institutional repositories, which are freely available on the web and also searchable via Google Scholar. You may be able to find recent dissertations on your research subject online!

Conferences and associations sometimes publish their proceedings and publications freely online. Search the organization's site to see if they have an archives page and/or past conference proceedings listed. They may also be accessible through Youtube or Google Scholar as well.

Secondary Sources:

If you have an idea from an author that is published in another author's text, you can cite it as a secondary source; however, do this sparingly. In graduate school, professors may prefer you to cite the original source. In this case, find the primary source, read it, and cite it directly rather than citing a secondary source. 

source: https://ulm.libguides.com/c.php?g=1414838&p=10482788