In People v. Guerrero (1988) 44 Cal. 3d 343, the Supreme Court previously had established evidentiary limitations on the "permissible scope of proof to establish the substance of a prior conviction, i.e., the nature and circumstances of the underlying conduct." Guerrero concluded that the trier of fact could "look to the record of the conviction-but no further . . . ." to establish the substance of the prior conviction. (Guerrero, supra, 44 Cal. 3d at p. 355) Thus, evidence other than the "record of conviction" may not be utilized to prove that appellant's 1981 conviction met the definition of a "serious felony."