Search for "sum-frequency generation (SFG)" in Full Text gives 2 result(s) in Beilstein Journal of Nanotechnology.
Beilstein J. Nanotechnol. 2016, 7, 374–405, doi:10.3762/bjnano.7.34
Beilstein J. Nanotechnol. 2014, 5, 2275–2292, doi:10.3762/bjnano.5.237