The following worked for me:
Reza Mansouri & Roman U. Sexl (1997) A test theory of special relativity: I. Simultaneity and clock synchronization, General Relativity and Gravitation, Volume 8, Issue 7, pp 497–513.
In essence, I recognized that Gen. Rel. Grav. was most likely the journal's name. (The other possibility was Sexl. Gen. Rel. Grav., but it seemed less likely, because S.U. Sexl. seemed likely to be the second author's name followed by a period.) Once I had found the journal, the year was most useful to me. I then guessed that 8 was the issue. This didn't turn up anything. (Later I discovered that 8 is the volumne.) Next, I guessed that 497 was a page reference, which guided be towards Issue 7. From their, I searched for (what I presumed was the first author's name) Mansouri, which gave me my result.