Pictures of personality : guide to the four human natures / John Lopker

 Lopker, John;

Los Angeles : Typology , 2000

Tempe : kumpulan fakta menarik berdasarkan penelitian

 Winarno; Winarno, Wida; Winarno, A. Driando Ahnan;

Jakarta : Gramedia Pustaka Utama , 2017