To cite package 'hht' in publications use:

Daniel Bowman (2014). The Hilbert-Huang Transform: Tools and Methods R version 3.0.1 (2013-05-16).

Corresponding BibTeX entry:

  @Manual{,
    title = {The Hilbert-Huang Transform: Tools and Methods},
    author = {Daniel C. Bowman and Jonathan M. Lees},
    year = {2014},
    note = {R version 3.0.1 (2013-05-16)},
  }