  We study the two-particle form-factors for the relativistic limit of the
integrable S-matrix of the mixed-flux AdS_3 X S^3 X T^4 string theory. The
S-matrix theory was formally constructed in two distinct ways by two different
teams. We focus on the massive theory built up by Frolov, Polvara and
Sfondrini, and derive expressions for the minimal solutions to the axioms, in
both integral and manifestly meromorphic form, and then proceed to apply the
off-shell Bethe ansatz method of Babujian et al. We obtain the integral
formulas for the two-particle complete form-factors and check the axioms at
this particle number.
