The heading Russian S.F.S.R. is used for both the Soviet Government for the period November 7, 1917-July 23, 1923, and for the constituent republic of the Soviet Union from 1923. The pre-AACR2 form for these entities in LC was Russia (1917- R.S.F.S.R.)
The heading Soviet Union is used for the Union of Soviet Socialist Republics from 1923. (Its pre-AACR2 form in LC was Russia (1923- U.S.S.R.)
The pre-AACR2 heading Russia (1917-1922. Civil War Governments) was used for the various counterrevolution governments. Each will be separately established whenever it is needed in post-1980 cataloging.
(Taken from Cataloging Service Bulletin, No. 20/Spring 1983; p. 37)
Now, the old names are still valid for the period 1917-1991:Russia (through 1917), Soviet Union (from 1917-1991), and Russian S.F.S.R. (from 1917-1991) are valid corporate headings, but Former Soviet republics is used only as a subject.
The Commonwealth of Independent States, used only as a corporate body, comprises eleven of the Former Soviet republics and is not the successor the the Soviet Union.
LC apparently changed its mind about establishing each counterrevolutionary government separately. The note to Russia (Territory under White armies, 1918-1920) reads:
This heading is used for all governments that contended with the Bolshevik government for control of the Russian empire during the period 1918-1920. Governments which were founded to control only a part of the empire, such as the Dalnevostochnaia Respublika and Vsevelikoe Voisko donskoe, are established independently. the Bolshevik government during this period is represented by the heading Russian S.F.S.R. NAFL5059050