US 3,856,386 A↗1974Assignee: Yashica Co., Ltd.Inventors: Yoshisato FujiokaYASHICA AUTO YASHINON-DS 20mm f/3.3— 11 ELEMENTS / 9 GROUPS, DESIGN f = 20.00 mm
JP 1975-110330 A↗1975Assignee: Yashica Co., Ltd.Inventors: Yoshisato FujiokaYASHICA ML 24mm f/2.8— 9 ELEMENTS / 8 GROUPS, 24mm f/2.8