Reference

1. http://purplepuplelicious.blogspot.co.id/2012/05/erd-entity-relaionship-diagram-pada-erd.html
2. https://herlinnairine.wordpress.com/2014/02/06/entity-relationship-diagram-erd-dan-contoh-kasus/
3. http://creately.com/diagram/example/h8zp7igm/Car%20dealer%20company
4. https://adyahmad334.wordpress.com/2015/12/19/erd-entity-relationship-diagram/
5. http://www.ilmumu.com/pengetahuan/pengertian-erd-dan-contohnya/
6. http://xzilin.blogspot.com/2012/11/jenis-atribut-tabel.html
7. http://blog-mini-indo.blogspot.com/2010/10/er-model-dalam-basis-data.html
8. http://hocuspocus23.blogspot.com/2014/02/tugas-erd-softskill.html
9. http://amandadewi13.blogspot.com/2014/01/soal-erd-softskill.html