@Article{LanguascoZaccagnini2010c, Author = "A. Languasco and A. Zaccagnini", Title = "On a {Diophantine} problem with two primes and $s$ powers of $2$", Journal = "Acta Arith.", Note = "\url{http://arxiv.org/abs/0811.3663}", Year = 2010, Abstract = "We refine a recent result of Parsell (2003) on the values of the form $\lambda_1 p_1 + \lambda_2 p_2 + \mu_1 2^{m_1} + \dots + \mu_s 2^{m_s}$, where $p_1$, $p_2$ are prime numbers, $m_1$, \dots, $m_s$ are positive integers, $\lambda_1 / \lambda_2$ is negative and irrational and $\lambda_1 / \mu_1$, $\lambda_2/\mu_2 \in \mathbb{Q}$." }