This is the first of three volumes presenting the works of Mark Grigorievich Kreĭn previously unavailable in English translation. Mark G. Kreĭn (Kyiv, 1907 – Odessa, 1989) was one of the foremost mathematicians of the twentieth century. His seminal contributions to functional analysis, operator theory, and related areas have had a profound and lasting influence on modern mathematics and continue to inspire contemporary research.

The present volume contains articles originally published between 1926 and 1937. It also includes a biographical essay by Inna Rikun and a complete bibliography of Kreĭn’s works.