???? ??????? ??????? ???????? ??? ??????? ??? ??? 1955. ??? ????? ???????? ??????????? ??? ??????? ?????? ????????? ?????????? ????????ɡ ??????? ???? ??????? ????????? ??????. ??? ???????? 230????? ????? ?? ??? 1998? ???? 3?110 ????? ????? ??????? ????? ?85?119 ????? ????? ??????? ?????. ??? ????? ???? ????? ??????? ??????? ??????? ????? ??????? ?????.

???? ????? ??????? ?????????? ?????????? ????????? ???????: ????? ??????? (1980)? ????? ????? ?????? ????????? (1985)? ????? ??? ????? ???? ???????? ??????? ?????? (1986)? ????? ??? ???????? ??????? ?????? ??????? ????????? ??????????? (1989).