By Karlson, Paul.
Barcelona Editorial Labor 1960 .
744 p., [2] p. of plates , Título original: Vom Zauber der Zahlen. 22 cm..

By Karlson, Paul.
Barcelona Editorial Labor 1961 .
440 p., 7 leaves of plates (1 fold.) , Translation of Du und die Natur. 23 cm..

By Karlson, Paul.
Barcelona Editorial Labor 1966 .
p. , Translation of : Vom Zauber der Zahlen.