Repopulation: is it inevitably?
  A mathematical model of radiotherapy is proposed. The study used the classical 24 hours way of fractionation with a weekend pause. We introduce the matrices of ``radiotherapy'' and ``growth''. We developed an equation of the fraction cell evolution, which we solved numerically. The results indicate that the accelerated growth of cells occurs due to the decrease of the fraction of slowly growing cells and increase of the cells that are fast growing. 
K. Malachowski, M. Wolf