On formal power series defined by infinite linear systems
\textit{W. Kuich} and \textit{F. J. Urbanek} [Theor. Comput. Sci. 22, 95-126 (1983; Zbl 0516.68059)] defined a class of noncommutative formal power series by considering a certain type of infinite linear systems; in the present note, we give a simple construction which shows that each formal power series is in this class. So the closure properties of the above paper are trivially verified.
scientific article; zbMATH DE number 3872688