<a href="https://en.wikipedia.org/wiki/Bell_P-39_Airacobra" class="extiw" title="w:Bell P-39 Airacobra">P-39K-1 and P-39L-1</a>: General arrangement, right and left sides
<a href="https://en.wikipedia.org/wiki/United_States_Army_Air_Forces" class="extiw" title="w:United States Army Air Forces">United States Army Air Forces</a>
1944-04-12
"Pilot's flight operating instructions for army models P-39K-1 and P-39L-1airplanes", p. 5 (<a rel="nofollow" class="external text" href="http://www.wwiiaircraftperformance.org/P-39/P-39K-1_L1_Operating_Instructions.pdf">PDF</a>)