Edmund Gettier: Wikipedia entry on this thinker and his Problem.
FOLDOC: Gettier Problem: Detailed article by Luciano Floridi from this philosophical database.
Is Justified True Belief Knowledge?: Gettier's classic paper from the journal Analysis, 1963.
The Gettier Problem: 2001 student paper by Sara Smollett, attempting through improved definitions to recover the definition of knowledge as justified true belief.
UMass Philosophy: Gettier: His official faculty page at the University of Massachusetts. Includes minimal profile.