:: deftheorem defines *' IDEAL_1:def 21 :
for R being non empty doubleLoopStr
for I, J being Subset of R holds I *' J = { (Sum s) where s is FinSequence of the carrier of R : for i being Element of NAT st 1 <= i & i <= len s holds
ex a, b being Element of R st
( s . i = a * b & a in I & b in J ) } ;