Training age - influence on number of sets

In 1998 I wrote, published and claimed copyright on this concept (bolding added now):

The influence of training age on number of sets:

… a beginner is not likely to need any more than one to two sets per exercise to gain a training effect. It could be argued that the more advanced a trainee becomes, the more sets required. I believe this is true up to a point. There is a point in time where further increases in volume (no. of sets) will not benefit, and the search for further training effects should be limited to increases in intensity.

I was conducting research and I came upon the following exercise in a publication copyright claimed by another 'author' at a subsequent date (bolding added):

Training Age: a beginner to strength training is unlikely to need exposure to more than 1-2 sets of a given exercise….. And clearly the more advanced trainee needs greater volume, however this is only true up to a point. There is definitely a point of diminishing returns when it comes to total sets, and at this point further progress can only be made by increases in intensity.

And I said to myself: “That looks familiar!” So I cross-referenced it and I said to myself: “Wow! No wonder that looked familiar!”

And I came upon this wording another one more times by the same 'author' in different publications - in the absence of credits or references to the origin or permission to use from the original author (myself), and that the 'author' claimed copyright....