To cite adespatial in publications use:

  Dray S, Bauman D, Blanchet G, Borcard D, Clappe S, Guénard G, Jombart
  T, Larocque G, Legendre P, Madi N, Wagner HH (????). _adespatial:
  Multivariate Multiscale Spatial Analysis_. R package version 0.3-24,
  <https://CRAN.R-project.org/package=adespatial>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {{adespatial}: Multivariate Multiscale Spatial Analysis},
    author = {St{\'e}phane Dray and David Bauman and Guillaume Blanchet and Daniel Borcard and Sylvie Clappe and Guillaume Gu{\'e}nard and Thibaut Jombart and Guillaume Larocque and Pierre Legendre and Naima Madi and Helene H Wagner},
    note = {R package version 0.3-24},
    url = {https://CRAN.R-project.org/package=adespatial},
  }

When using constr.hclust() please use:

  Guénard G, Legendre P (2022). “Hierarchical Clustering with
  Contiguity Constraint in R.” _Journal of Statistical Software_,
  *103*(7), 1-26. doi:10.18637/jss.v103.i07
  <https://doi.org/10.18637/jss.v103.i07>.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {Hierarchical Clustering with Contiguity Constraint in {R}},
    author = {Guillaume Gu{\'e}nard and Pierre Legendre},
    journal = {Journal of Statistical Software},
    year = {2022},
    volume = {103},
    number = {7},
    pages = {1--26},
    doi = {10.18637/jss.v103.i07},
  }