The planck length Universal upper bound to entropy-to-energy ratio for bounded systems, Phys. Rev. D, vol.23, issue.3, pp.287-298, 1981. ,
A covariant entropy conjecture, Journal of High Energy Physics, vol.1999, issue.07, 1999. ,
DOI : 10.1088/1126-6708/1999/07/004
URL : http://arxiv.org/abs/hep-th/9905177