The serious leisure perspective: An introduction. Elkington S, Stebbins R. S Elkington, R Stebbins - 2014 - taylorfrancis.com GSID: 7PRRXhDTXkcJ
Zoos and tourism: Conservation, education, entertainment?. Frost W. W Frost - 2011 - books.google.com GSID: eZKCqSt1N6QJ