On biorthogonal expansions in exponential functions

An equiconvergence theorem for nonharmonic Fourier series of the form $\sum a_ne^{i\lambda_nx}$ and ordinary Fourier series is proved for functions in $L^p(-\pi,\pi)$, $p>1$, when the exponents $\{\lambda_n\}$ are the roots of a member of a certain class of entire functions.