Chen Wu and Lijuan Wang, Invariant Characters of Tolerance Class and Reduction under Homomorphism in IIS. journal = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology. January 2017, vol. 123(3). 135 - 139 [viewed 25 April 2024]. Available from: https://publications.waset.org/pdf/10008418.