ProtoSMILES defines a fixed set of chemical element symbols that even at the time of publication was partially obsolete ]. The symbol for element 105 is given as Ha (Hahnium), despite IUPAC's resolution of the naming controversy of the element in favor of the symbol Db (Dubnium) years prior . Balsa therefore disallows the symbol Ha. To maintain compatibility with Proto-SMILES and avoid future changes to Balsa's grammar, elements having atomic number greater than 105 are also excluded.