Tensor products and independent sums of $\Cal L_p$-spaces, $1<p<\infty$

Two methods of constructing infinitely many isomorphically distinct $\Cal L_p$-spaces have been published. In this article we show that these constructions yield very different spaces and in the process develop methods for dealing with these spaces from the isomorphic viewpoint. We use these methods to give a complete isomorphic classification of the spaces $R_p^\alpha$ constructed by Bourgain, Rosenthal, and Schechtman and to show that $X_p\otimes X_p$ is not isomorphic to a complemented subspace of any $R_p^\alpha.$