New York TImes: A new book says Moscow acquired the secret of the hydrogen bomb not from its own scientists but from an atomic spy at the Los Alamos weapons lab in New Mexico. Historians call its case sketchy but worthy of investigation, saying the book, “The Nuclear Express: A Political History of the Bomb and its Proliferation,” by Thomas C. Reed and Danny B. Stillman, adds to a growing number of riddles about who invented the Soviet H-bomb a half century ago.