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Aggie = Agnieszka?

Sorry for nitpicking :)

But from what I know, part of Poles (about 30% or so) pronounce it as Russian hard "л". I am not sure about the figures, though, since I don't have that book anymore.
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Your friend is mostly correct, but in these sounds, he is a bit off.
"c'" sounds very much like Russian "ч"
"cz" has no exact match in Russian; there is a similar sounds in Bielorussian, though -...