1-Cordes,K.,Ibrahim,H.,M. (1999). Aplication in Recreation & Leisure for Today and future. Second Edition. Boston WCB / McGraw-Hill Comp.
2- Jenkins J. M., Pigram, J., J., (2003) Encyclopedia of Leisure and Outdoor Recreation Routledge, London
3- Virden,R.,J.(2006) Outdoor and Advanture Recreation, Human kinetics (editor) Introduction to Recreation and Leisure. Human Kinetics, Champaign.
4- Buckley, R., (2006) Advanture Tourism, CABI, Oxfordshire