Douglas print ad from 1961 showing space vehicle concepts.
URL: http://cgi.ebay.com/1961-DOUGLAS-Missiles-SPACE-SYSTEMS-Lunar-Vehicles-Ad-/310237049775?pt=LH_DefaultDomain_0
URL: http://cgi.ebay.com/1961-DOUGLAS-Missiles-SPACE-SYSTEMS-Lunar-Vehicles-Ad-/310237049775?pt=LH_DefaultDomain_0