AHM Shamsuzzoha and Tauno Kekäle and Petri Helo, Towards External Varieties to Internal Varieties − Modular Perspective. journal = {International Journal of Industrial and Manufacturing Engineering}, [online]. World Academy of Science, Engineering and Technology. May 2009, vol. 29(5). 306 - 312 [viewed 26 April 2024]. Available from: https://publications.waset.org/pdf/3981.