Use arabic numerals for volume numbers if the work cited includes more than 1 volume, even if the publisher used roman numerals.
1. US Department of Health and Human Services. Understanding and Improving Health and Objectives for Improving Health. Vol 1. 2nd ed. Washington, DC: US Dept of Health and Human Services; 2000.
If the volumes have separate titles, the title of the volume referred to should be given first, with the title of the overall series of which the volume is a part given in the final field, along with the name of the general editor and the volume number, if applicable.
2. Kleiss W, Marcus C, Wabitsch M, eds. Obesity in Childhood and Adolescence. Leipzig, Germany: Karger; 2004. Pediatric and Adolescent Medicine; vol 9.
In example 2 above, Pediatric and Adolescent Medicine is the name of the entire series; Obesity in Childhood and Adolescence is the ninth volume.
When a book title includes a volume number or other identifying number, use the title as it was published. Note: The volume number does not need to be repeated in its customary place after the year if it is included in the book’s title.
3. Field Manual 4–02.17: Preventive Medicine Services. Washington, DC: US Dept of the Army; 2000.
4. US Veterans Health Administration/Department of Defense. Clinical Practice Guidelines: Diabetes Mellitus Algorithms—Module F: Foot Care. Washington, DC: Veterans Health Administration; 2003.