Skizzen und Text, Frei Otto = Ancient architects : what could the ancient master builders have invented? : a contribution to the history of inventing structures on the road to architecture / drawings and text, Frei Otto. -- Institut für Leichte Flächentragwerke, c1994. -- (Mitteilungen des Instituts für Leichte Flächentragwerke (IL) Universität Stuttgart / Leitung, Frei Otto = Information of the Institute for Lightweight Structures (IL) University of Stuttgart / director, Frei Otto ; 37).