We prove that if A is a subset of those primes which are congruent to 1 3 such that the relative density of A in this residue class is larger than 12, then every sufficiently large odd integer n which satisfies n 0 3 can be written as a sum of three primes from A. Moreover the threshold of 12 for the relative density is best possible.
Ali Alsetri (Tue,) studied this question.