Columbia subject headings:
Elskamp, Max, 1862-1931.
Mockel, Albert, 1866-1945.
Harvard subject headings:
Elskamp, Max, 1862-1931.
Mockel, Albert, 1866-1945.
Princeton subject headings:
Elskamp, Max, 1862-1931.
Mockel, Albert, 1866-1945.