The downtown subarea regulations in Chapter 12.64 BMC comprise zoning regulations which are unique to the downtown subarea, except where other regulations in this title are adopted by reference. The downtown subarea regulations reside in a document, entitled the “Downtown Subarea Plan and Regulations,” which is formatted differently and bound separately from the other regulations in this title. The downtown subarea regulations utilize district zoning classifications unique to this subarea, which zoning classifications are denoted in color in the downtown subarea plan and regulations but are assigned letter symbols for city-wide zoning classification mapping purposes as follows: