​Working Paper No. 480 Central counterparties and the topology of clearing networks, Marco Galbiati and Kimmo Soramäki, August 2013. Bank of England.

“Given a network of client-clearer relationships, we define central clearing as a function transforming bilateral trading exposures into centrally cleared exposures.  By using numerical simulations, we study how this function is affected by the network’s topology, focusing on the exposures of the central counterparty.  By assuming that margin requirements are a linear function of exposures, we also draw conclusions as to how the network topology affects aggregate margin requirements.”