After having done an exercise about forming gen. plural of nouns I have discovered a rule not found before in my books: Feminine nouns ending in -я preceded by a consonant form their gen. plural with -ь. No exception is found in the exercise proposed by Auburn University: неделя -> недель; песня ->песень; туфля (туфли)-> туфель; капля -> капель. My spirit has fall down when I finally have found hidden in a remote corner of a remote place of my dictionary that "this rule is OK save after н". And gives as an example песня ->песен, following so the general rule: книга -> книг. Perhaps it is rather an academical question. I think that my dictionary is right, but, what do you think of it all ? Thanks