Avraham Goldstein Petr Kolman Jie Zheng Minimum Common String Partition Problem: Hardness and Approximations. 484-495 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3341&spage=484 2004 conf/isaac/2004 ISAAC db/conf/isaac/isaac2004.html#GoldsteinKZ04