etc.

From an interview with Julius Schulman (source):

"Now, at that time also, there was a man name of Fred Dapprich. Fred Dapprich was a very well known man. He worked with [Rudolf M.--Ed.] Schindler and some of the early architects." 

"...Neutra gave me other assignments to photograph in the ensuing months. Neutra introduced me to other architects who were active in the post-depression years--Gregory Ain, Rudolf Schindler, J. R. Davidson, Harwell Harris."

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"[Schindler's given names] are Rudolph Michael: He disliked the first, was called by the second, and for thirty-two years practiced architecture as R.M. In the office we called him R.M." (McCoy 1960 pvii)

Schindler's grand-daughter: Margot Schindler-Ehrens (Warren 2011 p 370)