I would find it very helpful if the vocabulary lists for the lessons included all of the new words used, including Russian spelling and pronunciation. For example, in Lesson 4, the vocabulary list doesn't include the words for "can" and "credit card" which are very useful for travelers. I'm aware that frequently there are often conjugation and usage issues, etc., but perhaps these could just be briefly noted in the pdf's.
Overall, I'm enjoying the series. Nice job!