Speed - defined

In 2000 I wrote, published and claimed copyright on this concept (bolding added now):

Speed can be defined as the time taken between two points.

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):

Speed can be defined as the time taken between two points.

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

Published 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....