Sidon-type inequalities for Legendre polynomials (Q1897520)

After the paper by \textit{R. Bojanić} and \textit{Č. V. Stanojević} [Trans. Am. Math. Soc. 269, 677-683 (1982; Zbl 0493.42011)], there has been an explosion of interest in Sidon inequalities and their use to investigate \(L^1\)-convergence of certain types of Fourier series. This paper obtains an analogue of these results for the Legendre-Dirichlet kernels and applies it to obtain integrability conditions for the Legendre-Fourier series of an even function.