chapter one business letters(商务信函) 1.1 introduction 1.2 writing guide 1.2.1 the essentials of business letter writing 1.2.2 the structure of business letters 1.2.3 the formats of a business letter 1.2.4 the format of envelopes 1.3 letters for example 1.3.1 letter one 1.3.2 letter two 1.3.3 letter three 1.3.4 letter four 1.4 words and phrases 1.5 notes 1.6 useful expressions 1.7 exercises chapter two establishing business relations(建立业务关系) 2.1 introduction 2.2 writing guide 2.3 letters for example 2.3.1 an introduction of an ex