. . "Not all spies walk on two legs, some of history's most successful sleuths fly, bark, and swim. Animals have become undercover heroes in the military, on the police force, and even in the CIA!" . . . . . . . . . . "The Cold War pigeon patrols and other animal spies"@en . "Juvenile works"@en . . . "Juvenile works" . "The Cold War pigeon patrols and other animal spies" . . .