premise: Nathan Never is a black-and-white, science fiction Italian comic book, published monthly in Italy since 1991 by Sergio Bonelli Editore. It is written by Michele Medda, Antonio Serra and Bepi Vigna. Artists who worked to series include Claudio Castellini, Roberto De Angelis, Dante Bastianoni, Nicola Mari, Pino Rinaldi, Giancarlo Olivares and Onofrio Catacchio.
hypothesis: Nathan Never is published 12 times a year.
reason: The context clearly says the comic book is "published monthly in Italy since 1991." As there are 12 months in a year, it would only make sense that it is published each of those months, for the context to be true.