H.Matsunaga, T.Iida, T.Fukushima, T.Santa, H.Homma, K.Imai : Boron Trifluoride-Etherate (Lewis Acid) as an Efficient Acid at Cyclization/Cleavage Reaction of D/L-Amino Acid Affording the Retention of their Original Configuration in the Edman Sequencing Method of Peptides.