O’Connor, S., Campbell, R., Cortez, H., & Knowles, T., 2009, Whale Watching Worldwide: tourism numbers, expenditures and expanding economic benefits, a special report from the International Fund for Animal Welfare, Yarmouth MA, USA, prepared by Economists at Large. http://www.ifaw.org/whalewatchingworldwideArchyvuota kopija 2012-08-01 iš Archive.is projekto
ifaw.org
O’Connor, S., Campbell, R., Cortez, H., & Knowles, T., 2009, Whale Watching Worldwide: tourism numbers, expenditures and expanding economic benefits, a special report from the International Fund for Animal Welfare, Yarmouth MA, USA, prepared by Economists at Large. http://www.ifaw.org/whalewatchingworldwideArchyvuota kopija 2012-08-01 iš Archive.is projekto