Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         "crystal-kingdom"
           chemical substances
             reactive intermediates
               Class dipolar compounds
                 Class 1,3-dipolar compounds
                   Class Propargyl type 1,3-dipolar compounds [X≡N+-Z <-> X-=+N=Z <-> X-=NZ+ <-> XN=Z (X=C,O; Z=C,N,O)]
                     Class azides [RN=N+=-N]