$1![v'_O!8W!L,(B. $1!Os!0$!4W!0#!_A(B: $1!E{!1Ds - $1'=G!:es ($1'Kg!KE'7t'CU'_K'Xm!3K!JH!Nas, 1988)
Keywords: $1'_o'L4!;E'Xis