Não informado. (2019). Newsletter. Pennsylvania State University, Environmental Resources Research Institute.
Chicago-referens (17:e uppl.)Não informado. Newsletter. University Park, Pa: Pennsylvania State University, Environmental Resources Research Institute, 2019.
MLA-referens (8:e uppl.)Não informado. Newsletter. Pennsylvania State University, Environmental Resources Research Institute, 2019.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.