A Note on Entropy Relations of Black Hole Horizons
  We focus on the entropy relations of black holes in three, four and higher dimensions. These entropy relations include entropy product, "part" entropy product and entropy sum. We also discuss their differences and similarities, in order to make a further study on understanding the origin of black hole entropy at the microscopic level. 
Xin-he Meng, Wei Xu, and Jia Wang
gr-qc hep-th