Both volume and issue information, if present, is required in references for books and journals.
Books
A book that is part of a multivolume set will have a volume number in the reference. Abbreviate the word Volume as Vol. and Volumes as Vols. followed by the Arabic volume number. The volume number follows the title of the book and comes after the edition statement (when there is one), it is enclosed in parentheses.
Example:
Scott, L. (2011). Parental nutrition. Clinical nutrition (2nd ed., Vol. 3)....
Kyle, P. (2003). People and places (Vols. 1-5)...
Journals (7.01)
Both volume and issue numbers are required in references to journal articles. Not all journals have issue numbers.
Write all volume numbers as Arabic numerals and italicize (no abbreviation for volume). The issue number proceeds immediately after the volume and is not italicized. Place all issue information within parentheses.
Example:
5 is the volume number and 3 is the issue number: Advertising to Adolescents: An Examination of Skepticism. (2011). Global Journal of Business Research, 5(3), 85-91.
3 is the volume number and 4 is the issue number: Moreira, J. P. (2010, December). Health literacy: A new dimension for healthcare development. Journal of Marketing & Management in Healthcare, 3(4), 239-240.