The Russian verb bytˈ 'to be' has different functions in different constructions. It is argued that it therefore represents several different verbs. A number of tests applied to sentences containing bytˈ show that there are four such verbs: a tense marker, which is a surface structure insert, and three deep, or deeper, surface inserts: the copula, the form that links the subject with an adverb, and the true verb.
"'To Be' in Russian,"
Colorado Research in Linguistics: Vol. 2.
Available at: https://scholar.colorado.edu/cril/vol2/iss1/3