I have a document containing a SET of three equations. I want to number

them:

(3.12a), (3.12b) and (3.12c)

but I have no idea how to add the a, b and c to the automatic numbering

of the equations (I have some ideas on how to make sure the numbering

itself does not advance for two equations, using the equation counter)

Anybody have any ideas on this subject

Thanks a lot

Greetz

Kelly