The original paper
H. Saigo, “Category Algebras and States on Categories.”
has been published in the Special Issue “Quantum Fields and Off-Shell Science” of the online journal Symmetry to which Prof. Dr. Ohtsu, Director-in-Chief, RODreP serves as a Guest Editor (June 29, 2021).
Its PDF version can be downloaded from the URL below.
PDF Version: https://www.mdpi.com/2073-8994/13/7/1172/pdf