Some volumes have separataly numbered supplements.
Electronic reproduction. [Place of publication not identified] : HathiTrust Digital Library, 2010.
Master and use copy. Digital master created according to Benchmark for Faithful Digital Reproductions of Monographs and Serials, Version 1. Digital Library Federation, December 2002. http://purl.oclc.org/DLF/benchrepro0212
Vol. 56, no. 1 (Mar. 2006); title from contents screen (SpringerLink, viewed Oct. 7, 2011).