I was very happy to learn that Plenum Press has decided to publish an English edition of Chemistry of the Ionosphere. Although the book was largely intended for the Soviet reader in order to fill some gaps in Russian-language reviews on aeronomic problems, I hope that it may be useful to foreign specialists engaged in iono- spheric research as well. Naturally, during the time which has elapsed since the preparation of the Russian edition new studies have been published in the world literature on the problems dealt with in this book. The most important of these are noted in the ap- pendix to...