Measure Zero Stability Problem for Drygas Functional Equation with Complex Involution

In this chapter, we discuss the Hyers–Ulam stability theorem for the σ-Drygas functional equation $$\displaystyle f(x+y)+f\big (x+\sigma (y)\big )=2f(x)+f(y)+f\big (\sigma (y)\big ) $$ for all \((x,y)\in \varOmega \subset \mathbb {C}^{2}\) for Lebesgue measure m(Ω) = 0, where \(f:\mathbb {C}\to Y\) and σ : X → X is an involution.