"Elevators Whisk Tourist to Bottom of 750-Foot Cave" Popular Science, May 1932, drawings of visitor center and elevators "Creation of Carlsbad Cave National Monument".
"Elevators Whisk Tourist to Bottom of 750-Foot Cave"Popular Science, May 1932, drawings of visitor center and elevators نسخة محفوظة 05 يوليو 2014 على موقع واي باك مشين.