What is the first documented use of the term, "Systems Thinking"?

Although new historical discoveries can be made, as of this writing, the answer is 1938 in a book entitled, "Interpretations and Misinterpretations of Modern Physics" by Philipp Frank. There are many misconceptions and an abundance of misinformation on Google search of when the term "Systems Thinking" (or "System Thinking") was first used. This publication identifies the first documented use of the term. Note that the first use of the term is not the same as the first discussion of systems, systems, sciences, thinking about systems, complexity, etc. In this article, we are simply looking for the first documented use of the specific term.