Kishnani, Nirmal
BCI Asia, 2012
Buku Referensi
Nur Firdaus
Indonesian , 2015
Artikel Jurnal
Taysum, Alison
Emerald Publishing Limited, 2020
eBooks
Fikri Arrasyadi
Fakultas Ekonomi dan Bisnis Universitas Indonesia, 2019
UI - Skripsi Membership
edited by Ivonne Audirac
John Wiley and Sons, 1997
Buku Teks SO