The terms "additive" and "divisive" originate with Curt Sachs's book "Rhythm and Tempo" (1953), while the term "aksak rhythm" was introduced for the former concept at about the same time by Constantin Brăiloiu, in agreement with the Turkish musicologist Ahmet Adnan Saygun. The relationship between additive and divisive rhythms is complex, and the terms are often used in imprecise ways. In his article on rhythm in the second edition of the "New Grove Dictionary of Music and Musicians," Justin London states that: