Bartha , Éva, and Szilvia Perényi. “Communication of Trainers As One of the Means for Customer Retention in Fitness Clubs”. Applied Studies in Agribusiness and Commerce, vol. 9, no. 1-2, Sept. 2015, pp. 35-40, https://doi.org/10.19041/APSTRACT/2015/1-2/7.