Q. Hi, I was just wondering, how do you format the citation for a translated work if the name of the translator is not known?
A. For a book, you could adapt the usual format for translated titles (see CMOS 14.104), substituting information about the translation for the translator’s name. The fact that the name of the translator is not known could be added in square brackets. (Adapt as needed for other types of sources.)
Last Name, First Name. Title of Book in English. Translated from the Russian [translator unknown]. Chicago: University of Chicago Press, 1972.
The definite article in “Translated from the Russian” is conventional (it implies “from the Russian edition” or “from the Russian text”). Some editors will choose to omit it.