1. British Standard: Gravity drainage systems inside buildings. Roof drainage, layout and calculation: BS EN 12056-3:2000.
2. British Standard: Gully tops and manhole tops for vehicular and pedestrian areas. Definitions, classification, general principles of design, performance requirements and test methods: BS EN 124-1:2015.
3. Urban Drainage
4. Farouk, M. Z. 2017. “The Efficiency of A Depressed Gully Inlet of A Malaysian Drain.” Degree Thesis, Universiti Sains Malaysia.