1) Some books about the USSR available for free :
-Worker's participation in the Soviet Union (Mick Costello, 1977) : https://archive.org/stream/WorkersParticipationInTheSovietUnion/Workers%20Participation%20in%20the%20Soviet%20Union#page/n3/mode/2up
-Khrushchev Lied (Grover Furr, 2011) : https://archive.org/details/pdfy-nmIGAXUrq0OJ87zK/page/n1/mode/2up
-Worker's participation in the Soviet Union (Mick Costello, 1977) : https://archive.org/stream/WorkersParticipationInTheSovietUnion/Workers%20Participation%20in%20the%20Soviet%20Union#page/n3/mode/2up
-Khrushchev Lied (Grover Furr, 2011) : https://archive.org/details/pdfy-nmIGAXUrq0OJ87zK/page/n1/mode/2up
2)
-Human Rights in the Soviet Union (Albert Szymanski, 1984) : https://archive.org/details/HumanRightsInTheSovietUnion/page/n1/mode/2up
-Soviet Democracy (Pat Sloan, 1937) : https://archive.org/details/in.ernet.dli.2015.261348
-Socialism in the Soviet Union (Jonathan Aurthur, 1977) : https://archive.org/details/SocialismInTheSovietUnionByJonathanAurthur
-Human Rights in the Soviet Union (Albert Szymanski, 1984) : https://archive.org/details/HumanRightsInTheSovietUnion/page/n1/mode/2up
-Soviet Democracy (Pat Sloan, 1937) : https://archive.org/details/in.ernet.dli.2015.261348
-Socialism in the Soviet Union (Jonathan Aurthur, 1977) : https://archive.org/details/SocialismInTheSovietUnionByJonathanAurthur
-What Were the Chances To Be Sent to Gulag ? : https://www.northstarcompass.org/nsc0901/gulag.htm