To cite package 'occ' in publications use:

Radua J, Bullich S, Lopez N and Catafau AM. Restricted maximum likelihood estimation of PET neuroreceptor occupancy in the absence of a reference region. Medical Physics 2011;38:2558

Corresponding BibTeX entry:

  @Article{,
    author = {Joaquim Radua and Santiago Bullich and Natalia Lopez and
      Ana M Catafau},
    title = {Restricted maximum likelihood estimation of PET
      neuroreceptor occupancy in the absence of a reference region},
    journal = {Medical Physics},
    year = {2011},
    volume = {38},
    pages = {2558},
  }