Full Idea
The standard view is that Frege cases [knowing Jocasta but not mother] show that reference doesn't determine sense, and Twin cases [knowing water but not H2O] show that sense doesn't determine reference.
Gist of Idea
It is claimed that reference doesn't fix sense (Jocasta), and sense doesn't fix reference (Twin Earth)
Source
Jerry A. Fodor (The Elm and the Expert [1993], §1.3)
Book Reference
Fodor,Jerry A.: 'The Elm and the Expert' [MIT 1995], p.24
A Reaction
How about 'references don't contain much information', and 'descriptions may not fix what they are referring to'? Simple really.