©2013 National Research Council of Thailand
Sheldon และผู้แต่งคนอื่นๆ. 1999. Ecotourism development in northern Thailand : an exploration of perceptions and potentials. Faculty of Graduate Studies and Research, University of Alberta;
Sheldon และผู้แต่งคนอื่นๆ. (1999) Ecotourism development in northern Thailand : an exploration of perceptions and potentials . University of Alberta/Alberta.
Sheldon และผู้แต่งคนอื่นๆ. Ecotourism development in northern Thailand : an exploration of perceptions and potentials. . Alberta:University of Alberta, 1999.
Sheldon และผู้แต่งคนอื่นๆ. (1999) Ecotourism development in northern Thailand : an exploration of perceptions and potentials . University of Alberta/Alberta.