1. S. Weinberg, Infrared photons and gravitons, Phys. Rev. 140 (1965) B516 [ INSPIRE ].
2. R. Akhoury, R. Saotome and G. Sterman, Collinear and soft divergences in perturbative quantum gravity, Phys. Rev. D 84 (2011) 104040 [ arXiv:1109.0270 ] [ INSPIRE ].
3. C.W. Bauer, S. Fleming, D. Pirjol and I.W. Stewart, An effective field theory for collinear and soft gluons: heavy to light decays, Phys. Rev. D 63 (2001) 114020 [ hep-ph/0011336 ] [ INSPIRE ].
4. C.W. Bauer, D. Pirjol and I.W. Stewart, Soft collinear factorization in effective field theory, Phys. Rev. D 65 (2002) 054022 [ hep-ph/0109045 ] [ INSPIRE ].
5. M. Beneke, A. Chapovsky, M. Diehl and T. Feldmann, Soft collinear effective theory and heavy to light currents beyond leading power, Nucl. Phys. B 643 (2002) 431 [ hep-ph/0206152 ] [ INSPIRE ].