A. Santi:
A generalized integrability problem for G-Structures
Ann. Mat. Pura Appl. Vol. 195, N. 5, p. 1463-1489, 2016

A. Santi:
Almost CR quaternionic manifolds and their immersibility in HP^n
Abh. Math. Semin. Univ. Hambg. (Published Online) Vol. 87, N. 1, p. 83-103, 2017