Survey of India. "Refer to this map as: 1:20,000 Trivandrum guide map, first edition. Relief show by 10 metre contour (contours are approximate) interval and spot heights. Depths shown by soundings in meters. Published under the direction of Brigadier J. A. F. Dalal, Officiating Surveyor General of India. Verso: See Trivandrum (1:40,000) with relevant buildings shown pictorially.