Before revision: 400px|Parker Variable wing The Parker Variable Wing is a wing configuration in biplane or triplane aircraft designed by H.F. Parker in 1920The Parker variable wing , naca-report-77 , 1920.
After revision: 400px|Parker Variable wing The Parker Variable Wing is a wing configuration in biplane or triplane aircraft designed by H.F. Parker in 1920"The Parker variable wing ", NACA Report 77 , 1920.