To cite package ‘MetChem’ in publications use:

  Abdel-Shafy E, Melak T, MacIntyre D, Zadra G, Zerbini L, Piazza S,
  Cacciatore S (2023). _MetChem: Chemical Structural Similarity
  Analysis_. R package version 0.4,
  <https://CRAN.R-project.org/package=MetChem>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {MetChem: Chemical Structural Similarity Analysis},
    author = {Ebtesam Abdel-Shafy and Tadele Melak and David A. MacIntyre and Giorgia Zadra and Luiz F. Zerbini and Silvano Piazza and Stefano Cacciatore},
    year = {2023},
    note = {R package version 0.4},
    url = {https://CRAN.R-project.org/package=MetChem},
  }