Phonological question:

[kasak.livejournal.com]

Are the Russian sounds /ш/ and /ж/ retroflexed? They simply sound much harder to me than the English /sh/ and /zh/ sounds. Does anyone know for sure? Wikipedia, as nice as it is, doesn't really list its sources on this subject matter, so if someone could answer this from their own personal knowledge, or could point me to a website (in English or Russian) that details these sounds, that'd be great. Any help in getting a more accurate pronunciation of the /щ/ would also be appreciated!

Спасибо!