To cite package 'measuRing' in publications use:

Lara W, Bravo F, Sierra C (2015). “measuRing: An R Package to measure tree-ring widths from scanned images.” Dendrochronologia, 34, 43–50. doi:10.1016/j.dendro.2015.04.002.

Corresponding BibTeX entry:

  @Article{,
    title = {{measuRing}: An {R} Package to measure tree-ring widths
      from scanned images},
    author = {W. Lara and F. Bravo and C.A Sierra},
    journal = {Dendrochronologia},
    year = {2015},
    volume = {34},
    pages = {43--50},
    doi = {10.1016/j.dendro.2015.04.002},
  }