OBERTH, Hermann (1894-1989). Die Rakete zu den Planetenrumen. Munich and Berlin: R. Oldenbourg, 1923. 8o. 3 lithographed folding plates and numerous diagrams in text. Modern quarter cloth, original front wrapper bound in. FIRST EDITION. Norman 1604. -- OBERTH. Wege zur Raumschiffahrt. Munich and Berlin: R. Oldenbourg, 1929. 8o. 4 lithographed folding plates and numerous illustrations in text. Original tan cloth. Original pictorial dust jacket (some chipping to panels, mostly along edges). Third expanded edition of Die Rakete zu den Planetenrumen, "for many years the most authoritative theoretical work on rocketry" (Norman 1605). (2)