Dieter Lohmar
Springer Science, 2012
eBooks
Manen, Max Van
Routledge, 2016
eBooks
Banister, Peter
Open University Press, 1994
Buku Teks SO
Brouwer, Martinus Antonius Wesselinus, 1923-
Gramedia, 1984
Buku Teks SO
Buffalo : University of Buffalo
Majalah, Jurnal, Buletin