Mark Cieliebak Stephan Eidenbenz Paolo Penna Noisy Data Make the Partial Digest Problem NP-hard. 111-123 http://dx.doi.org/10.1007/978-3-540-39763-2_9 2003 conf/wabi/2003 WABI db/conf/wabi/wabi2003.html#CieliebakEP03