In this paper we have established the maximum number of constraints in a two-level orthogonal array of 192 runs of resolution VI.
Bodh Raj Gulati. "Construction of Two-level Saturated Symmetrical Factorial Designs of Resolution VI." Ann. Math. Statist. 43 (5) 1652 - 1663, October, 1972. https://doi.org/10.1214/aoms/1177692398