[GAP Forum] Image homomorphism(Tensor sqaure)

[Takjk Taj]

Dear GAP forum, 
Brown and Johnson Robertson proved in [*] 
for given a central extension
1 --> K ---> G ----> G/K ---->1
there is an exact sequence
(A\otimesK)x(K\otimes A) \Stackrel {l} ------> K\otimesK ---> G\otimes G ---> 1
in which Im(I) is central.
Can we calculate Im (l)  with GAP?
every suggestion is welcome.
Thanks
*. Some Computations of Non-Abelian Tensor
Products of Groups, JOURNAL OF ALGEBRA 111, 177-202 (1987).