If you are using the SHARC code, please cite the following references.
For the code:

• S. Mai, M. Richter, M. Ruckenbauer, M. Oppel, P. Marquetand, L. González
  SHARC: Surface Hopping Including Arbitrary Couplings – Program Package for Non-Adiabatic Dynamics, sharc-md.org (2014).

Please also do not forget to cite the references, where the method is described:

• M. Richter, P. Marquetand, J. González-Vázquez, I. Sola, L. González
  SHARC – ab initio molecular dynamics with surface hopping in the adiabatic representation including arbitrary couplings
  J. Chem. Theory Comput. 7, 1253-1258, (2011).
• S. Mai, P. Marquetand, L. González
  A General Method to Describe Intersystem Crossing in Trajectory Surface Hopping
  Int. J. Quantum Chem., 115, 1215-1231 (2015).

For your convenience, please find the references below in different formats.

BibTex:
@Misc{sharc-md,
Title = {SHARC: Surface Hopping Including Arbitrary Couplings — Program Package for Non-Adiabatic Dynamics},
Author = {Sebastian Mai and Martin Richter and Matthias Ruckenbauer and Markus Oppel and Philipp Marquetand and Leticia Gonz\’alez},
HowPublished = {sharc-md.org},
Year = {2014}
}
@Article{Richter2011JCTC,
Title = {{SHARC}: ab initio Molecular Dynamics with Surface Hopping in the Adiabatic Representation Including Arbitrary Couplings},
Author = {Martin Richter and Philipp Marquetand and Jes\'{u}s Gonz\'{a}lez-V\'{a}zquez and Ignacio Sola and Leticia Gonz\'{a}lez},
Journal = {J. Chem. Theory Comput.},
Year = {2011},
Number = {5},
Pages = {1253-1258},
Volume = {7},
Doi = {10.1021/ct1007394},
Url = {http://dx.doi.org/10.1021/ct1007394}
}
@Article{Mai2015IJQC,
Title = {A General Method to Describe Intersystem Crossing Dynamics in Trajectory Surface Hopping},
Author = {Sebastian Mai and Philipp Marquetand and Leticia Gonz\’alez},
Journal = {Int. J. Quantum Chem.},
Year = {2015},
Volume = {115},
Pages = {1215-1231},
Doi = {10.1002/qua.24891},
ISSN = {1097-461X},
Keywords = {surface hopping, intersystem crossing, nonadiabatic dynamics, photochemistry, spin-orbit coupling},
Url = {http://dx.doi.org/10.1002/qua.24891}
}

RIS:
TY – GEN
AU – Mai, Sebastian
AU – Richter, Martin
AU – Ruckenbauer, Matthias
AU – Oppel, Markus
AU – Marquetand, Philipp
AU – González, Leticia
T1 – SHARC: Surface Hopping Including Arbitrary Couplings — Program Package for Non-Adiabatic Dynamics
Y1 – 2014

ER –
TY – JOUR
AU – Richter, Martin
AU – Marquetand, Philipp
AU – González-Vázquez, Jesús
AU – Sola, Ignacio
AU – González, Leticia
T1 – SHARC: ab initio Molecular Dynamics with Surface Hopping in the Adiabatic Representation Including Arbitrary Couplings
JO – J. Chem. Theory Comput.
Y1 – 2011
VL – 7
IS – 5
SP – 1253
EP – 1258
UR – http://dx.doi.org/10.1021/ct1007394
M3 – 10.1021/ct1007394

ER –
TY – JOUR
AU – Mai, Sebastian
AU – Marquetand, Philipp
AU – González, Leticia
T1 – A General Method to Describe Intersystem Crossing Dynamics in Trajectory Surface Hopping
JO – Int. J. Quantum Chem.
Y1 – 2015
VL – 115
SP – 1215
EP – 1231
UR – http://dx.doi.org/10.1002/qua.24891
M3 – 10.1002/qua.24891
KW – surface hopping
KW – intersystem crossing
KW – nonadiabatic dynamics
KW – photochemistry
KW – spin-orbit coupling
U1 – 1097-461X