Affiliation: | AEI, West Texas A & M University, BOX 248, Canyon TX 79016, USA, US ?bo Akademi University, Department of Business Administration, Henriksgatan 7, FIN-20500 ?BO, Finland E-mail: ralf.ostermark@abo.fi, FI Department of Mathematics, West Texas A & M University, Canyon TX 79016, USA, US Department of Computer Science, Beijing University, Beijing 100080, China, CN
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