Cite this article:

. . New Technology of Library and Information Service, 1993, 9(1): 48-51.

URL:

https://manu44.magtech.com.cn/Jwk_infotech_wk3/EN/10.11925/infotech.1003-3513.1993.01.12     OR     https://manu44.magtech.com.cn/Jwk_infotech_wk3/EN/Y1993/V9/I1/48