Nlend, Samuel, and Theo G. Swart. “Multi-level Optical On-Off Line Code for Flat-like Power Spectral Density: Outdoor Visible Light Communications”. ECTI Transactions on Electrical Engineering, Electronics, and Communications 21, no. 3 (October 28, 2023): 251466. accessed August 28, 2026. https://ph02.tci-thaijo.org/index.php/ECTI-EEC/article/view/251466.