Special issues called "Numero extraordinario" accompany some volumes.
Electronic reproduction. [S.l.] : 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
Mode of access: World Wide Web.
Description based on: No. 504/505 (enero/feb. 1993); title from digital reproduction of cover (publisher’s Web site, viewed Aug. 23, 2002).