def read_files(self, reference=None):
        """
        Read all the pdb file in the inputfiles list, creating SASModels.
        The SASModels created are save in a list, the reference model is the first model in the list.

        :param reference: position of the reference model file in the inputfiles list
        """
        ref = reference if reference is not None else 0
        inputfiles = self.inputfiles

        models = []
        models.append(SASModel(inputfiles[ref]))
        for i in range(len(inputfiles)):
            if i==ref:
                continue
            else:
                models.append(SASModel(inputfiles[i]))
        self.models = models

        return models