Please cite the paper below for the dagLogo package.

  Ou J, Liu H, Nirala N K, et al. dagLogo: An R/Bioconductor package
  for identifying and visualizing differential amino acid group usage
  in proteomics data[J]. Plos one, 2020, 15(11): e0242030.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {dagLogo: An R/Bioconductor package for identifying and visualizing differential amino acid group usage in proteomics data},
    author = {{Ou} and {Jianhong} and {Liu} and {Haibo} and {Nirala} and Niraj K and {Stukalov} and {Alexey} and {Acharya} and {Usha} and {Green} and Michael R and {Zhu} and Lihua Julie},
    journal = {Plos one},
    volume = {15},
    year = {2020},
    number = {11},
    pages = {e0242030},
    url = {https://doi.org/10.1371/journal.pone.0242030},
    doi = {10.1371/journal.pone.0242030},
    publisher = {Public Library of Science San Francisco, CA USA},
  }