The terms gender dysphoria and gender identity disorder were not used until the s, [27] when Laub and Fisk published several works on transsexualism using these terms. Wegener writes, "Langevin makes several concrete suggestions regarding the language used to describe sexual anomalies. Studies in Swaab , Gooren , Garcia-Falgueras , and Rametti confirmed earlier research findings that gender identity is influenced by brain structure. A study by Chung suggested significant sexual dimorphism in the BSTc did not become established until adulthood, theorizing that either changes in fetal hormone levels produce changes in BSTc synaptic density and other factors which later lead to the observed differences in BSTc, or the differences are affected by the generation of a gender identity inconsistent with assigned sex.