Proceedings of the National Academy of Sciences of the United States of America, Vol. 14, No. 12 (Dec. 15, 1928), pp. 911-914 (4 pages) ...
Measure and Integral, Banach and Hilbert Space, Linear Integral Equations. By Prof. Adriaan Cornelis Zaanen. (Bibliotheca Mathematica: a Series of Monographs on Pure and Applied Mathematics. Volume 2.