Seach Engines. Invisible Web: What it is, Why it exists, How to find it, and Its inherent ambiguity. What is the "Invisible Web", a.k.a. the "Deep Web"?
The "visible web" is what you can find using general web search engines. It's also what you see in almost all subject directories. 10 Google Operators for Advanced Search I Use Daily (and You Should Too)
The Harvard Library Innovation Laboratory at Harvard Law School.