In putting together an archive, you will almost invariably find gaps. It also helps to supplement records and memory, in some cases, with newspaper clippings or other items to support what you have. This helped immeasurably in creating the Dick Davy Archive and the running list of his appearances.
FREE:
Archive.org: There are countless comedy-related items to be found here, and likely some comedy-only collections, as well
Google Newspaper Archive: This hasn’t been updated in a while, as they stopped scanning new papers a few years ago, but you may find some things here of use
Elephind.com: Access to worldwide newspapers
The paid/subscription services often do have what you can’t find elsewhere, but the results are often limited, in scope. We encourage you to see if the loose search results you see yield anything first to see if it is worth digging. Some of these sites offer free trial periods, as well.
PAID / SUBSCRIPTION SERVICES (many are available free through your local library):
Newspapers.com
Newspaperarchive.com
NewYorkTimes.com
NewYorker.com