Natura - nature
Ref: C. Linnaeus, 1748: 210
   actualia - actual entities
  Ref: A. Voltolini, 2006: 44 (note 19) [assumed position]
     Mundus Plinius - physical world
    Ref: C. Linnaeus, 1758: 5 [indirect position]; 24 Apr 2014.
       naturalia - natural bodies
      Ref: C. Linnaeus, 1758: 6 [implicit position]
         "crystal-kingdom"
        Ref: J.D. Dana, 1863: 1 [indirect position]
           chemical substances
          Ref: G.J. Leigh et al., 1998: 7 [implicit position]
             chemical compounds
            Ref: Wikimedia: 27 Sep 2009
               Class selenonic acids [RSe(=O)2OH]
              Ref: G.P. Moss et al., 1995: 1365