Klopotan, I., K. Vrhovec-Žohar, i E. Mahič. „Relationship Between Customers’ Loyalty and Income: Preliminary Research“. ENTRENOVA - ENTerprise REsearch InNOVAtion, sv. 1, izd. 1, listopad 2015., str. 65-70, https://hrcak.srce.hr/ojs/index.php/entrenova/article/view/14386.