García Fernández, J., P. Gálvez Ruíz, A. Bernal García, and L. Vélez Colón. “Economic Expenditure in Low-Cost Fitness Centers: Differences According to the Loyalty and Characteristics of the Client”. SPORT TK-EuroAmerican Journal of Sport Sciences (March 21, 2016): 137–144. Accessed September 27, 2026. https://revistas.um.es/sportk/article/view/254141.