A manual for writers of research papers, theses, and dissertations, 7th edition - Kate L. Turabian 2007

Search for sources systematically - Look for someone who knows something about your topic
Finding useful sources
Part I. Research and writing: from planning to production

As you search for sources, you must be knowledgeably systematic, because if you miss an important one, you'll lose credibility.

3.3.1 Look for someone who knows something about your topic

You might start by asking around to find someone who knows something about your topic and standard reference works on it: advanced students, faculty, even people outside the academic community. You might look up your topic in the yellow pages of the phonebook. You won't always find someone, but you might get lucky.