In determining the sufficiency of the affidavit, we are bound by the four corners of the document. Gaston v. State, 440 S.W.2d 297 (Tex.Cr.App. — 1969) (Onion, J., concurring), cert. denied, 396 U.S. 969, 90 S.Ct. 452, 24 L.Ed.2d 435; Wetherby v. State, 482 S.W.2d 852 (Tex.Cr.App. — 1972). Examining the affidavit in such manner, we hold that it does reflect adequate probable cause and sufficient 'underlying circumstances' to satisfy the requirements of Aguilar v. Texas, 378 U.S. 108, 84 S.Ct. 1509, 12 L.Ed.2d 723. Appellant's first ground of error is overruled.