You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Russian_language

Context:
The Northern Russian dialects and those spoken along the Volga River typically pronounce unstressed /o/ clearly (the phenomenon called okanye/оканье). Besides the absence of vowel reduction, some dialects have high or diphthongal /e~i̯ɛ/ in the place of Proto-Slavic *ě and /o~u̯ɔ/ in stressed closed syllables (as in Ukrainian) instead of Standard Russian /e/ and /o/. An interesting morphological feature is a post-posed definite article -to, -ta, -te similarly to that existing in Bulgarian and Macedonian.

Question:
What do some Russian dialects do about vowels?

absence of vowel reduction