I'm running into review problems because of the different spellings of 不过 bu2guo4/bu4guo4. eg., this lesson [ http://popupchinese.com/lessons/elementary/digital-volleyball ] says bu2guo4, while this one [ http://popupchinese.com/lessons/elementary/the-lecture-circuit ] says bu4guo4.

The problem comes with the pinyin review. Absent context, there's no way of knowing which lesson the word is drawn from. So if I see 不过, I have to guess whether bu2guo4 or bu4guo4 is the correct answer; I'm wrong half the time.