Any one read this book. It was an Ace paperback by Don Benson who is unfortunately diceased. Humanoid Aliens come to earth in 1908 near Tunguska(sp?)-YES, THAT one. They interact with Earthers and cause things like to election of Edison to US President, cure WilhelmII's withered arm AND Nicholas's son Alexei's hemophilia. They then go into hibernation and wake up with BIG changes like spaceships. Teddy Roosevelt was killed in a moonrocket accident.You may have to check either used book stores or SF Conventions. 