Shelton purchased an automobile on credit from Erwin. Both Shelton and Erwin clearly intended to create a security interest in the car in favor of Erwin. As a consequence, they signed a bill of sale that set out the terms of payment of the balance due and that also required that Shelton insure the auto until paid for in full. Shelton later obtained a title certificate from the state that clearly showed Erwin as the holder of a first lien on the car. Did these actions and documents give Erwin a security interest in the car? (Shelton v. Erwin, 472 F.2d 1118)