The first reference in the book is a quote from George Thomas himself (below). The second reference is quoting the article you printed above.
What I say in the book avec Thomas quotes is this:
Having the good fortune to be surrounded by many world class designers certainly aided his rise to the elite level of the field. Beyond the list of Philadelphia architects, Mr. Thomas had occasion to study with Donald Ross.
"On the green committee of the Philadelphia Cricket Club I aided in the work on their reconstructed course, and in the building of their new Flourtown course, the first being done under the supervision of Donald Ross, the second from the designs of A.W. Tillinghast, both golf architects of the highest class. Before this, and as a member of the Sunnybrook Committee in Pennsylvania, I was connected in its construction with…Donald Ross."
While he was able to observe the numerous elements which comprise the creation of courses, Thomas was particularly impressed with the way Ross used detailed drawings to plan the layout.
"The first accurate plans I saw were those of Donald Ross, when I worked on a green committee where he laid out the course. This did me a lot of good, for up to that time, as noted, the work had been without definite scheme."
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I don't recall this being discussed elsewhere in the book. It's possible but I don't think so.
Thank you for another good spirited post Sven. Bonhomie is, after all, golf's greatest element. I'm a big fan of anybody that boosts our game in that regard.