Hamad, M. . S. . ., Hamza, I. A. . and Al-Muktar, S. . A. . . (2010) “Influence of sucrose and tyrosine on callus induction and morphine and codeine production on Papaver somniferum In vitro”, Journal of Biotechnology Research Center, 4(2), pp. 45–53. doi: 10.24126/jobrc.2010.4.2.120.