To cite cosa in publications use:

Bulus, M. & Dong, N. (2018). cosa: Bound Constrained Optimal Sample Allocation. R package version 1.2.1. https://CRAN.R-project.org/package=cosa

Corresponding BibTeX entry:

  @Manual{,
    title = {{cosa}: Bound Constrained Optimal Sample Allocation},
    author = {Metin Bulus and Nianbo Dong},
    note = {R package version 1.2.1},
    year = {2018},
    url = {https://CRAN.R-project.org/package=cosa},
  }