Ibrahim, Yusuf, et al. “Some Reliability Characteristics of a Linear Consecutive 2-Out-of-4 System Connected to 2-Out-of-4 Supporting Device for Operation”. International Journal of Engineering & Technology, vol. 7, no. 1, Feb. 2018, pp. 135-9, https://doi.org/10.14419/ijet.v7i1.8037.