CLAMP is an all-female Japanese manga artist group, consisting of leader and writer Nanase Ohkawa from Osaka, and three artists whose roles shift for each series: Mokona, Tsubaki Nekoi, and Satsuki Igarashi from Kyoto.

Here is a useful link to the works of CLAMP;
https://en.wikipedia.org/wiki/List_of_Clamp_works

This series were published between 1990-1996
This is in excellent condition.