说明：  自然语言理解──　一种让机器懂得人类语言的研究 （第2版）自然语言理解──　一种让机器懂得人类语言的研究 （第2版）
(-- a machine to understand human language to study the natural language understanding (Second Edition)-- a machine to understand human language to study the natural language understanding (Second Edition)-- a machine to understand human language to study the natural language understanding (Second Edition))