15.1 Periodical abbreviations will follow Bridson's Botanico- Periodicum-Huntianum/ Supplementum (BPH) (Pittsburgh; Hunt Institute, 1991). The book abbreviations will follow Stafleu & Cowan's Taxonomic Literature, ed.2 (TL-2) (Utrecht, Bohn, Scheltrema & Holkema, 1976), but the convention for capitalization will be consistent with BPH. In case of uncertainty as to what abbreviations should be used, the questions will be decided on a case by case basis by the editorial committee.