Fluorescent bulbs have an advantage in that they are more energy-efficient than conventional bulbs. On this light bulb you'll find a GR10q socket.
From Amazon
Osram 16w 2D Square 4-Pin GR10q Cap Standard White (3500k) Compact Fluorescent Lamp, GR10
Big on Electricals
Osram 16w CFL Square 2D Bulb GR10Q Cool White - 816876