Googling the title works for reasonably new papers. Not so good for textbooks, old papers (titles used to be a lot less expressive 50 years ago), conference pro

Googling the title works for reasonably new papers. Not so good for textbooks, old papers (titles used to be a lot less expressive 50 years ago), conference proceedings (often not indexed by article anywhere, and the name of the volume can be ambiguous), grey literature like lecture notes (a URL would allow you to use the Wayback Machine). Also, don't count on authors to get the title right.