REPLACEMENT BULB FOR PHILIPS SL/018, SL18, SL18/27, SL18/O18 | eBay
Lighting-Gallery.net - My Lamps SL/Comparison between two Philips SL Prismatic 18W with base B22 and E27
Compact fluorescent lamp | Science Museum Group Collection
Philips SL*9 CFL with black base, early rare example of original CFL or energy saver design dating back to early 1980s, later lamps had a white base Stock Photo - Alamy
Integral compact fluorescent lamp | Smithsonian Institution