$1';1!K}'HW'Xl'4}!R]'Xl!G*s - $1!Cs!Tk!6<!Oz'Q[!UNs ($1!4I!0a'Xl!X7':`!^z!3K!JH!Nas, 1990)
Keywords: $1'U<!BX!BX!G*!+5'HW'Xl!BX!G*s