Don't know where to start with your research? Have no idea what to write about? Want an expert in your discipline to provide you with pertinent information and suggestions?
Start with a specialized encyclopedia or handbook!
Professors may have told you not to use "encyclopedias" in your research. They were probably referring to general encyclopedias (like Britannica), not the specialized, topical encyclopedias that may be highly valuable as you explore your topic.
Specialized encylopedias are written by experts in the field and will provide you with both overviews of and context for your topic while suggesting narrower topics to explore as well. Use the references and bibliographies included therein to find more sources on aspects that interest you.
Save both energy and time by exploring these reference sources!
The Cambridge encyclopedia of the English language by 
Cambridge grammar of the English language
The Oxford companion to the English language
The Cambridge history of the English language
The Cambridge history of medieval English literature by 