To cite shelltrace in publications use:

  de Winter, Niels J. (2017). ShellTrace v1.0 - A new approach for
  modelling growth and trace element uptake in marine bivalve shells:
  Model verification on pacific oyster shells (Crassostrea gigas)
  Geoscientific Model Development Discussions, gmd-2017-137 URL
  https://www.geosci-model-dev-discuss.net/gmd-2017-137

A BibTeX entry for LaTeX users is

  @Article{,
    title = {ShellTrace v1.0 - A new approach for modelling growth and trace element uptake in marine bivalve shells: Model verification on pacific oyster shells (Crassostrea gigas)},
    author = {Niels {de Winter}},
    journal = {Geoscientific Model Development},
    year = {2017},
    number = {gmd-2017-137},
    url = {https://www.geosci-model-dev-discuss.net/gmd-2017-137},
  }