It was published on PLos ONE and totally freeeeeeeeeeeeeeeeeeee / L3 T, S$ z, m) ~Peng T , Qinghua M , Zhenning T , Kaifa W , Jun J , 2011 Long-Term Sphere Culture Cannot Maintain a High Ratio of Cancer Stem Cells: A Mathematical Model and Experiment. PLoS ONE 6(11): e25518. doi:10.1371/journal.pone.0025518