("In a diversity case state law provides the elements of the plaintiff's case.” (citation omitted)). 5 . On appeal, Dupree also asserts that Valero is liable as a manufacturer of TAME, but these claims are not supported by a fair reading of the pleadings in this case. Moreover, because causation is also an essential element of a products liability claim, our analysis of Dupree’s negligence claim is dispositive of his products liability claim. 6 . See Fed. R.App. P. 28(a)(9) (requiring appellant's brief to include "the argument, which must contain ... appellant’s contentions and the reasons for them, with citations to the authorities and parts of the record on which the appellant relies”); see also L & A Contracting Co. v. S. Concrete Servs. Inc., 17 F.3d 106, 113 (5th Cir.1994)
holding that an argument that fails to cite to supporting authority in support of claim presents nothing for review holding that an appellant waived a claim where he failed to cite any legal authority in support of an argument in his appellate brief holding an argument waived for failure to cite authority holding that a failure to advance any argument or cite any supporting authority on a subject enables us to deem the issue waived holding argument waived for failure to raise it in opening brief