References: Procedures for the Collection of Diagnostic Blood Specimens by Venipuncture (H3-A6), 3rd Edition published by the National Committee for Clinical Laboratory Standards.
Kubagawa H, Gathings WE, Levitt D, Kearney JF, Cooper MD. Immunoglobulin isotype expression of normal pre-B cells as determined by immunofluorescence. J Clin Immunol. 1982;2:264-269.