Norhazwani M. Y. and  Khoo and  C. F. and  Hasrul Nisham R.,  Optimization Technique in Scheduling Duck Tours.   journal   = {International Journal of Humanities and Social Sciences}, [online]. World Academy of Science, Engineering and Technology.
    October 2011, vol. 58(10). 1241 - 1244
    [viewed 18 January 2020]. Available from: https://publications.waset.org/pdf/9001.