APA

Luhmann N., Baecker D. & Gilgen P. (2013). Introduction to systems theory. Cambridge, UK: Polity Press.

Chicago

Luhmann Niklas, Baecker Dirk and Gilgen Peter. 2013. Introduction to systems theory. Cambridge, UK: Polity Press.

Harvard

Luhmann N., Baecker D. and Gilgen P. (2013). Introduction to systems theory. Cambridge, UK: Polity Press.

MLA

Luhmann Niklas, Baecker Dirk and Gilgen Peter. Introduction to systems theory. Cambridge, UK: Polity Press. 2013.