Double dot product of 4th order tensor

I am trying to make a material model for my FEM code and
while deriving Elasticity tensor I found a term where I have to do some
tensor operation. It is as below

P:C:PT  where all the terms are 4th
order tensors. Now I konw the result of this should be a 4th order
tensor only as this term is in addition with other 4th order terms. Here
any (A:B) indicates Double dot product between A and B. 

Please help me out with this if you know or suggest some
good tensor calculus book where I can refer for my problem.

Thanks.