Y. Aserrar and E. Elqorachi, Cosine and sine addition and subtraction law with an automorphism, Ann. Math. Sil. 38 (2024), no. 2, 155–176.
Google Scholar
J. Dhombres, Relations de dépendance entre les équations fonctionnelles de Cauchy, Aequationes Math. 35 (1988), no. 2–3, 186–212.
Google Scholar
B. Ebanks, The cosine and sine addition and subtraction formulas on semigroups, Acta Math. Hungar. 165 (2021), no. 2, 337–354.
Google Scholar
B. Ebanks, Some Levi-Civita functional equations on semigroups, Results Math. 77 (2022), no. 4, Paper No. 154, 19 pp.
Google Scholar
E. Elqorachi and A. Redouani, Solutions and stability of generalized Kannappan’s and Van Vleck’s functional equations, Ann. Math. Sil. 32 (2018), no. 1, 169–200.
Google Scholar
R. Ger, On an equation of ring homomorphisms, Publ. Math. Debrecen 52 (1998), no. 3–4, 397–417.
Google Scholar
R. Ger, Ring homomorphisms equation revisited, Rocznik Nauk.-Dydakt. Prace Mat. (2000), no. 17, 101–115.
Google Scholar
R. Ger, Additivity and exponentiality are alien to each other, Aequationes Math. 80 (2010), no. 1–2, 111–118.
Google Scholar
R. Ger and L. Reich, A generalized ring homomorphisms equation, Monatsh. Math. 159 (2010), no. 3, 225–233.
Google Scholar
R. Ger and M. Sablik, Alien functional equations: a selective survey of results, in: J. Brzdęk et al. (eds.), Developments in Functional Equations and Related Topics, Springer Optim. Appl., 124, Springer, Cham, 2017, pp. 107–147.
Google Scholar
H. Stetkær, Functional Equations on Groups, World Scientific Publishing Co. Pte. Ltd., Singapore, 2013.
Google Scholar
H. Stetkær, Extensions of the sine addition law on groups, Aequationes Math. 93 (2019), no. 2, 467–484.
Google Scholar
H. Stetkær, The equation f(xy) = f(x)h(y) + g(x)f(y) and representations on ℂ^2, Aequationes Math. 98 (2024), no. 5, 1419–1438.
Google Scholar