Ewing. AMNH Bulletin Volume XXXII-1913, Article V, Part I pp. 93-121, plus two b&w plates: New Acarina. General Considerations and Descriptions of New Species from Minnesota, Wisconsin, and Michigan. AMNH Volume XXXVII-1917, Article II, Part II, pp. 149-172: New Acarina. Descriptions of New Species and Varieties from Iowa, Missouri, Illinois, Indiana, and Ohio. These articles disbound from complete volume.