I tried to explain this before and i didn't do such a great job so after a little more investigation I’ll have another stab at it:
3 forms A, B, and C
derived from 3 tables tbl A, tbl B, and tbl C.
tbl A : 1 <--> many : tbl B :1< --> many : many tbl C
Frm C embedded in Frm B embedded in...