To cite reshape in publications use:

Hadley Wickham (2007). Reshaping Data with the reshape Package. Journal of Statistical Software, 21(12), 1-20. URL http://www.jstatsoft.org/v21/i12/.

Corresponding BibTeX entry:

  @Article{,
    title = {Reshaping Data with the {reshape} Package},
    author = {Hadley Wickham},
    journal = {Journal of Statistical Software},
    year = {2007},
    volume = {21},
    number = {12},
    pages = {1--20},
    url = {http://www.jstatsoft.org/v21/i12/},
  }