In the erstwhile Soviet Union, lot of publishes from Moscow like Mir, Progress, Raduga, Peace & FLPH were quite prolific in publishing books on maths, science & popular science. Many of their books were translated into English. After dismatling of the Soviet Union, these piblishers & their books went into oblivion. The books are quite difficult to get niw. Here is a collection of 25 books in PDF format with OCR, bookmarks & covers:

A Planet of Riddles (Mir,1974)
A Visit to Transurania (Mir,1974)
Can Man Change Climate (Progress,1973)
Cybernetics Within Us (Peace,1966)
Einstein (Mir,1960)
Entertaining Electronics (Mir,1984)
Essays About the Universe (Mir,1985)
How People Discovered the Shape of the Earth (Raduga,1984)
How Reliable Is The Brain (Mir,1960)
Man and Nature (Progress,1980)
On the Way to Super-Elements (Mir,1986)
Physiology for Everyone by Boris Sergeev (Mir,1973)
Secrets of the Second World War (Progress,1971)
Sounds and Signs (Mir,1969)
The Atomic Nucleus (FLPH,1958)
The Code of Life (Peace,1966)
The Forces of Nature (Mir,1967)
The Moon and Man (Peace,1967)
The Mystery of Earth's Mantle (Peace.1966)
The Nine Colours of the Rainbow (Mir,1966)
The Quiet Sun (Mir,1968)
The Races of Mankind (FLPH,1964)
The Rliddle of the Self (Progress,1976)
The Sky Will Be Blue (Mir,1984)
Things to ome - Collected Articles (Mir,1977)
 
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