Koizumi wrote some books on judo, including Judo: The basic technical principles and exercises, supplemented with contest rules and grading syllabus (1958) and My study of Judo: The principles and the technical fundamentals (1960).
その後、小泉は『Judo: The basic technical principles and exercises, supplemented with contest rules and grading syllabus』（1958年）、 『My study of Judo: The principles and the technical fundamentals』（1960年）など柔道に関する本を書いた。