ecker, K., Becker, M.,& Schwarz, J. H.(2006). Strin theory and M-theory: A dern introduction. Caride university press. 22. West, P.(2001). E11 and M theory. Classical and QuantuGravity, 18(21), 4443. 23. Gopakur, R.,& Vafa, C.(1998). M-theory and topoloical strins--II. arXiv preprint hep-th/9812127.