Reference: McGregor 2010

McGregor, William B. 2010. Optional ergative case marking systems in a typological-semiotic perspective. Lingua 120(7). 1610–1636. Elsevier.

@article{mcgregor2010optional,
  author    = {McGregor, William B},
  journal   = {Lingua},
  number    = {7},
  pages     = {1610–1636},
  publisher = {Elsevier},
  title     = {Optional ergative case marking systems in a typological-semiotic perspective},
  volume    = {120},
  year      = {2010}
}