Senthil Kumar, K., and D. Malathi. “A Novel Method to Represent Access Tree Structure by Context Free Grammar With and-or Graph in Key Policy Based Attribute Based Encryption”. International Journal of Engineering & Technology, vol. 7, no. 4.10, Oct. 2018, pp. 396-8, https://doi.org/10.14419/ijet.v7i4.10.20946.