1. Time Flies for Drosophila
Audra L Scully, Steve A Kay 
Cell 
Volume 100, Issue 3, Pages (February 2000)
DOI: /S (00)

2. Figure 1 The Circadian Oscillator in Drosophila
Depiction of the interlocked feedback loops of the central pacemaker and the clock's response to light. Arrows indicate positive regulation and lines ending in bars denote negative regulation. R, repressor; A, activator; CCRE, circadian clock regulatory element; and ccg, clock controlled gene.
Cell  , DOI: ( /S (00) )