private IEnumerable <SessionPareOfWords> MixWords(IEnumerable <IPareOfWords> words)
{
words = wordManager.MixWords(words);
words = wordManager.CangeHalfTranslations(words.Cast <SessionPareOfWords>());
words = wordManager.MixWords(words);
return((IEnumerable <SessionPareOfWords>)words);
}