US 4596886, Hasegawa, Ryuichi & Kohji Hayashi, "Polyester containing impure 1,2-butanediol", published 1986-06-24, assigned to Mitsubishi Monsanto Chemical Company
.
US 4966658, "Recovery of ethylene glycol from butanediol isomers by azeotropic distillation", published 1990-10-30
. US 5423955, "Separation of propylene glycol from 1,2-butanediol by azeotropic distillation", published 1995-06-13