Studying verbal stems I see some questions that I beg you to confirm or correct, since what follows is my perception of the matter:
1) Every verb has a basic stem, that got from 3rd. p. pl. pre. ind.: готов-ят, жив-ут, читай-ут. That stem will give birth, after some taxed modifications, result of combination rules, to a "modificated stem" from which we can get past and infinitive tenses:
готов(+и)-ят ->готови-ть, готови-л ; жив(-в)-ут, жи-ть, жи-л, читай(-й)-ут, чита-ть, чита-л. The vocals having been taken (if any) from the infinitive and adding for past and for infinitive endings acording to some rules.
This present tense stem is got not having in mind consonant changes, so пиш-ут -> пис-ут -> пис(а)-ут -> stem: писа-. And infinitive becomes (of course) писа-ть and past писа-л. In other places I have been seen that this verb has two stems: пиш- and писа-. Strictly, in the measure of one must go to infinitive to look for some information...
2) So, only after having made the adjustments mentioned, and seen that they don't stick to reality, we can say that we are in front of a verb having two or even three stems (each of them giving source to patterns for some verbal forms). However after so a wide consideration of formation of tenses perhaps it will be difficult to find a "two stems verb", apart from хотеть and his friends .
My question rises of the fact that I have read in other place that in general verbs have two stems. Are there many heresies in these opinions?
Thanks