Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         "crystal-kingdom"
           chemical substances
             chemical compounds
               Class hydrazides [RkE(=O)l(OH)m (l≠0; ≥1 (OH):=(=NRNR2))]
                 1 Class carbohydrazides [RC(=O)NHNH2]
                 2 Class phosphonic dihydrazides [RP(=O)(NHNH2)2]
                 3 Class sulfonohydrazides [RS(=O)2NHNH2]