In addition, there are 3 compounds from the listed substances with mass spectra not available in the database. One of them, 2-formyl-1,1-dimethylhydrazine, which is a UDMH transformation product, was described in several studies . Substances such as 2-methyl-1H-imidazole-1-propanamine and 5-ethyl-1H-pyrazole-3-amine may be transformation products, but because their mass spectra are not available in Nist17, their identification may be extremely difficult. Their mass spectra are presented in Fig. . Adding mass spectra to the NIST database is also important for more accurate prediction of mass spectra by machine learning methods. If there is no mass spectrum in the database, then predicting the mass spectra of the candidate structure and comparing it with the experimental one can be very useful to further identify and weed out the false candidate.