P. Ramana  and  K. Alice Mary and  M. Surya Kalavathi and  M. Phani Kumar,  Design of a Non-linear Observer for VSI Fed Synchronous Motor.   journal   = {International Journal of Electrical and Computer Engineering}, [online]. World Academy of Science, Engineering and Technology.
    August 2011, vol. 56(8). 928 - 931
    [viewed 19 January 2020]. Available from: https://publications.waset.org/pdf/3403.