Triangle congruence criteria: Why not SSA?
In this applet you can vary the size of the angle, and the next two consecutive sides in the Triangle.
Notice that sometimes there are two possible triangles, and other times there are only one. The fact that there are sometimes two possible triangles means that we cannot use SSA to prove triangle congruence.
Observation
When DOES Angle-Side-Side work? Why DOESN'T it work all the time?