This is the original proposed structure by Zinke and Ziegler in
Chemische Berichte 77, 264 (1944).
In 1994, a special issue about the 50th anniversary of the proposal of
the macrocyclic structure of calixarenes was published in:
Journal of Inclusion Phenomena and Molecular Recognition in Chemistry, 19,
In this issue there can be found the review "The Early History of Calixarene Chemistry"
by Th. Kappe on pages 3-15.