ANURAK THANYACHAROENtran. 2026. A GENERALIZATION OF THE STABILITY OF A QUARTIC FUNCTIONAL EQUATION IN QUASI-β-NORMED SPACES WITH THE FIXED POINT METHOD. Journal of Mathematical Analysis. 17, 01 (Jul. 2026), 68–85. DOI:https://doi.org/10.5281/9sdkzd34.