During the summer semester of 1963, Keipert attended lectures at Marburg University, particularly with Herbert Bräuer, another one of Vasmer's students.
1999), he employs a functionalist approach (ultimately based on ideas by Alexander Isachenko and Nikolai Trubetzkoy) by describing the process of standardization as a gradual acquisition of the four features of a standard language as proposed by the Prague linguistic circle: polyvalence (i.e. ability to be used in all spheres of communication); stylistic differentiation; codification in grammars, dictionaries and phrase books; and general obligatoriness.
Thus, he can describe when the Russian standard language came to be used in each text type and therefore became more and more polyvalent in the course of the centuries (e.g. being used by artisans and merchants since the Middle Ages but only in 1876 for the translation of the Bible).
This approach is an inspiring alternative to traditional descriptions of the history of standard languages, which emphasize either the development of a linguistic norm or of a ‘high’ register.
His works show how many grammatical conceptions had been developed earlier mainly at the Academy of Sciences in Saint Petersburg (e.g. by Glück, Paus, Schwanwitz, or Adodurov) and thus ultimately borrowed from Western Europe.