Back about 30-40 years ago, I posed a problem in Mathematics Magazine (or maybe the Monthly) asking whether any triangle could be linked to a non-congruent similar triangle via a sequence of triangles, each "SSA-congruent" to the one before and the one after. There was a cute solution that pointed out that this is impossible because two SSA-congruent triangles have the same X, where X was some triangle statistic (like perimeter, inradius, or circumradius, but slightly less well-known) that scales linearly under similarity. Can anyone (a) figure out what X was, or (b) locate my problem and the solution? Jim Propp PS: In my original submission I proposed the term "ASS-congruent", which struck me as both more pronounceable and more apt, but the stodgy problems editor who reigned at the time deemed this too vulgar.