This Resource Letter provides a guide to the literature about intelligent life beyond the human sphere of exploration. It offers a starting point for professionals and academics interested in participating in the debate about the existence of other technological civilizations or in the search for extraterrestrial intelligence (SETI). It can also serve as a reference for teaching. This Letter is not intended as an exhaustive bibliography, but several extensive bibliographies have been cited. The letter E after an item indicates elementary, nontechnical material of general interest to persons becoming informed in the field. Intermediate level material, of a somewhat more specialized nature, is indicated by the Letter I. The annotation A indicates advanced, technical material. An asterisk (*) precedes items to be included in an accompanying Reprint Book.

中文翻译：

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资源信 ETC-1：外星文明

本资源信函为有关人类探索范围之外的智慧生命的文献提供了指南。它为有兴趣参与关于其他技术文明的存在或寻找外星智慧 (SETI) 的辩论的专业人士和学者提供了一个起点。也可作为教学参考。这封信的目的不是作为详尽的参考书目，而是引用了一些广泛的参考书目。项目后的字母 E 表示对该领域知情的人普遍感兴趣的基本非技术材料。具有更专业性质的中级材料用字母 I 表示。注释 A 表示高级技术材料。