PG2900 - PG3698 is the Library of Congress Subclassifiction range for Russian Literature. Within that range, LC has assigned each author a specific PG number or range of numbers, bringing together all materials by and about that author. Because the University of Chicago's Russian Literature collection predated the final development of the Library of Congress scheme for PG, previous to 2000, University of Chicago call numbers for Russian authors were assigned independently of LC's numbers.
In 2000, Regenstein Library decided to begin using the numbers assigned by the Library of Congress. Unfortunately, there are significant differences between the Regenstein numbers and LC's numbers. Thus, within Regenstein's Russian Literature section there are two separate call number ranges for authors published prior to 2000, and the books in each range can be located many shelves apart. Authors who began publishing after 2000 have only one call number range. Over time, as currently received books are cataloged using the LC numbers, more and more of Regenstein's Russian literature collection will be represented by the newer LC numbers.
In Regenstein bookstacks, works by and about Anna Akhmatova can be found under the following call numbers: PG3551.O72 and PG3476.A324.
Particularly if you are browsing, in order to review all of the relevant holdings pertaining to most Russian authors, you will need to identify both call number sequences.