$1![k!0s!5E'2>!BM!BX(B. $1!;E!6-'\O!_As - $1'c+!5w!3K!JH!C\!^v!3'!5-'Q['[M!\ks ($1'c+!5w!3K!JH!C\!^v!3'!5-s, 1988)
Keywords: $1!BM!BX!+9'_9'Oy!+5!Bs'X<s