http://wenku.baidu.com/link?url=CA7llUzU7NPsdHzeK1-95ZPJIuy93avlHVx8mKIjO1Pb5qz_NaZ467eRIGY6TBdLWsVCNnI3As3sfwhyEkOsZp0iyn6vPzdYqZdCotlFgHi
混合积的符号
http://baike.baidu.com/link?url=Gap5VyDY5PQWf8rL6OPd9JR55DsC0FxTWUCCcmgPMXqR3AqWYrBa-M_uHH2FEA4lnR6d4iJwCOkFbsCENKIdya
原文:http://www.cnblogs.com/lilei9110/p/3529937.html