To cite package 'hht' in publications use:

Daniel Bowman (2012). The Hilbert-Huang Transform: Tools and Methods R version 2.15.2 (2012-10-26).

Corresponding BibTeX entry:

  @Manual{,
    title = {The Hilbert-Huang Transform: Tools and Methods},
    author = {Daniel Bowman},
    year = {2012},
    note = {R version 2.15.2 (2012-10-26)},
  }