Question: Which document is the main regulatory text of the Soviet Union?
Paraphrase: Which report is the most administrative content of the Soviet Union?
SPARQL (Wikidata):  select distinct ?obj where { wd:Q15180 wdt:P92 ?obj . ?obj wdt:P31 wd:Q49848 } 
Answer: Declaration of the USSR Council of the Republics regarding the establishment of the Commonwealth of Independent States