Maldive Islands To Sumatera (Sumatra). Indian Ocean. International Chart Series INT 707. Admiralty Chart 4707. 18 January 1974. Scale 1:3,500,000. Small Corrections to 11 February 1976 [printed] and 1976 1690 [hand-stamped violet]. Printed August 1976.
Sumatra Northern Sheet ISTD Edition 1944. Northern Sumatra Geology after Zwierzycki (1919) simplified with amendments in Bireuen & Toba Lake areas & south of Langsaa. Compiled & drawn ISTD. February 1944. I.S.T.D./F/367