Errors in DOI indexing by bibliometric databases

DOI-i.e., Digital Object Identifier-is a character string, which univocally identifies entities that are object of intellectual property. In bibliometrics, DOIs are used for univocally identifying scientific papers. The aim of this short communication is to raise the reader's awareness of bibliometric database errors in DOI indexing, in particular, the incorrect assignment of a single DOI to multiple papers. This error is quite interesting since DOI is commonly regarded as an effective means to identify scientific articles unambiguously. For the purpose of example, a short list of DOIs, which have been wrongly assigned by the Scopus database to multiple papers, is shown. Although being relatively rare, DOI indexing errors should be considered by bibliometricians when querying bibliometric databases by DOI.