RE: Block versus diagonal omega

Everyone - Thank you all for your assistance in answering my question regarding the block versus diagonal omega structure. The answers that you all provided have been a great help thus far and are much appreciated. As a follow-up, I was curious if someone could point me towards a reference that would help me to figure out how to restructure the covariance into different omega blocks. Specifically, I would like to understand the basis and proper method for restructuring the omega block so that I may remove selected covariance terms when simplifying from a completely unstructured block to a more parsimonious one. Thanks again for your help and time - Al Berg