Local Axies

Hi all, I am trying to load polygon data from a file. I can do this fine apart from one thing- when a polygon is rotated and then saved to file in the program i am loading from, it shows that rotation by having a local axis for that polygon. I don''t know how to get the rotation about x, y and z from that axis- so when I load data, the polygons rotation is never loaded. How can I do this? I would have thought it would be fairly easy to find the rotation about x, y, and z from the local axis, but i''ve tried for ages and just cannot do it. Any ideas anyone?? Thanks in advance! Dave