Author:Mildred Clingerman

Barthold Fles
The copyright/acknowledgments for includes:
 * Mildred Clingerman Stair Trick. Copyright 1952 by Fantasy House, Inc. Reprinted by permission of Barthold Fles.

It's not clear what the relationship between and  is. Barthold Fles' Wikipedia entry says that he lived in the USA from 1925 to 1986 and that he was a literary agent meaning it's possible Mildred Clingerman was one of his clients and that he gave the reprint permission as her literary agent.

Similarly, the copyright/acknowledgment for the first german publication of The Good Provider by, see here has an addition with the sense: 'with kind permission of Barthold Fles'.