Peter M. G. Apers Alan R. Hevner S. Bing Yao Optimization Algorithms for Distributed Queries. 57-68 1983 9 IEEE Trans. Software Eng. 1 db/journals/tse/tse9.html#ApersHY83 http://doi.ieeecomputersociety.org/10.1109/TSE.1983.236170