All the negations of PL(X) satisfying the extension principle and the generalized extension principle are fully described through the negation of L. Necessary and sufficient conditions are given for n to be an ortho or u-complementation and for n to satisfy the DeMorgan laws.
@article{urn:eudml:doc:38842, title = {Negaciones en la teor\'\i a de conjuntos difusos.}, journal = {Stochastica}, volume = {5}, year = {1981}, pages = {33-44}, zbl = {0516.94033}, mrnumber = {MR0625840}, language = {es}, url = {http://dml.mathdoc.fr/item/urn:eudml:doc:38842} }
Esteva, Francesc. Negaciones en la teoría de conjuntos difusos.. Stochastica, Tome 5 (1981) pp. 33-44. http://gdmltest.u-ga.fr/item/urn:eudml:doc:38842/