To cite spfda in publications use:

  Wang, Z, Magnotti, JF, Beauchamp, MS. Li, M, Functional Group Bridge
  for Simultaneous Regression and Support Estimation.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {Functional Group Bridge for Simultaneous Regression and Support Estimation},
    author = {Zhengjia Wang and John F. Magnotti and Michael S. Beauchamp and Meng Li},
    journal = {arXiv},
    year = {2020},
  }