The format currently allows up to three place : publisher groups. This device is seldom found in bibliographical formats, but permits the accurate display and indexing of each element without recourse to a clumsy arrangement of notes and added entries. It is not often needed, and is currently most frequently encountered in art books published jointly by Chinese and non-Chinese publishers.
#410 北京|9bei jing
#411 東京|9toukyou_j
#420 文物出版社|9wen wu chu ban she
#421 平凡社|9heibonsha_j
ISBD: 北京 : 文物出版社 ; 東京 : 平凡社
#410 香港|9xiang gang
#411 [廣州]|9guang zhou
#420 香港書譜出版社|9xiang gang shu pu chu ban she
#421 廣東人民出版社|9guang dong ren min chu ban she
ISBD: 香港 : 香港書譜出版社 ; [廣州] : 廣東人民出版社
#410 Knokke
#411 台北|9tai bei
#420 Mappamundi Publishers
#421 南天書局|9nan tian shu ju
ISBD: Knokke : Mappamundi Publishers ; 台北 : 南天書局
It is unusual to find more than one publisher in the second place : publisher group; only 84 have been found to date (15 January 2016):
#410 北京|9bei jing
#411 香港|9xiang gang
#420 中國佛教協會|9zhong guo fo jiao xie hui
#421 香港寶蓮禪寺|9xiang gang bao lian chan si
#421a中國佛教文化出版有限公司|9zhong guo fo jiao wen hua chu ban you xian gong si
ISBD: 北京 : 中國佛教協會 ; 香港 : 香港寶蓮禪寺 : 中國佛教文化出版有限公司
More than two place : publisher groups are rarer still; there are currently only 10 in the catalogue (15 January 2016):
#410 北京|9bei jing
#411 上海|9shang hai
#412 天津|9tian jin
#420 文物出版社|9wen wu chu ban she
#421 上海書店|9shang hai shu dian
#422 天津古籍出版社|9tian jin gu ji chu ban she
ISBD: 北京 : 文物出版社 ; 上海 : 上海書店 ; 天津 : 天津古籍出版社