APA Style

Sumardy, . et al (2011). Customer loyalty playbook : how net promoter increases loyalty, advocacy & financial growth (Cet. 1). Jakarta: Upnormals Publishing.

MLA Style

Sumardy, . et al. "Customer loyalty playbook : how net promoter increases loyalty, advocacy & financial growth". Cet. 1 Jakarta: Upnormals Publishing, 2011. Text.