Some Petri Net Languages and Codes. - Masami Ito; Yoshiyuki Kunimochi (Developments in Language Theory, 2001)

Algebraic Properties of Petri Net Languages and Codes - Yoshiyuki Kunimochi (2009)

Algebraic Properties of Petri Net Morphisms based on Place Connectivity. - Yoshiyuki Kunimochi (AFL, 2011)

Some Properties of Extractable Codes and Insertable Codes. - Yoshiyuki Kunimochi (Int. J. Found. Comput. Sci., 2016)