Responsa for Chullin 46:29

R. Hayyim Eliezer further exchanged correspondence with R. Isaac b. Eliah concerning the following problems: An animal whose gall was removed; Blood that was seen by a woman following childbirth; A chicken that was cooked with milk; and a levir's rights of inheritance.
R. Isaac b. Eliah mentions that during his time, the Levirate marriage was not practiced in France.