To cite termstrc in publications use:

Robert Ferstl, Josef Hayden (2010). Zero-Coupon Yield Curve Estimation with the Package termstrc. Journal of Statistical Software, 36(1), 1-34. URL http://www.jstatsoft.org/v36/i01/.

Corresponding BibTeX entry:

  @Article{,
    title = {Zero-Coupon Yield Curve Estimation with the Package
      {termstrc}},
    author = {Robert Ferstl and Josef Hayden},
    journal = {Journal of Statistical Software},
    year = {2010},
    volume = {36},
    number = {1},
    pages = {1--34},
    url = {http://www.jstatsoft.org/v36/i01/},
  }