On Time Variations of Gravitational and Yang-Mills Constants in a   Cosmological Model of Superstring Origin
  In the framework of 10-dimensional "Friedmann-Calabi-Yau" cosmology of superstring origin we show that the time variation of either Newton's gravitational constant or Yang-Mills one is unavoidable in the present epoch. 
V. D. Ivashchuk and V. N. Melnikov
gr-qc