If authorship has not already been established, perhaps it can be determined through the signature. Don't despair if the artist's signature is hard to read, or the artist used only his initials. Well-known artists such as Rembrandt or Van Gogh would be listed in CPL's computerized card catalog. Not all artists are documented in book form. This is especially true of minor artists or young, emerging artists, although these occasionally may be written up in periodicals.
Art prices are more or less determined by the auction market.
To ascertain the worth of an artist's work, consult auction records. It's best to track activity over a number of successive years. You will sometimes find that auction records are the only source of information available on an artist. By the time this goes to press, there may be additional sites. If an artist's work never shows up at auctions, there may not be much of a market for it.