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Low-thrust trajectory design & optimization

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Initial design of low-thrust trajectory
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[1] A. E. Petropoulos and J. M. Longuski. Shape-Based Algorithm for the Automated Design of Low-Thrust, Gravity Assist Trajectories. Journal of Spacecraft and Rockets. 2004, 41(5):787-796

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A good summarize of low-thrust trajectory optimization
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[2] J. T. Betts. Survey of Numerical Methods for Trajectory Optimization. Journal of Guidance, Control and Dynamics. 1998, 21(2):193-207

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Direct method
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[3] Fahroo and I.M. Ross. Direct Trajectory Optimization by a Chebyshev Pseudospectral Method. Journal of Guidance, Control and Dynamics. 2002, 25(1):160-166
[4] J. T. Betts. Optimal Interplanetary Orbit Transfers by Direct Transcription. The Journal of the Astronautical Sciences. 1994, 42(3):247-268

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Hybrid method
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[5] G. Hull. Conversion of Optimal Control Problems into Parameter Optimization Problems. Journal of Guidance, Control and Dynamics. 1997, 20(1):57-60
[6] M. R. Ilgen. Hybrid Method for Computing Optimal Low Thrust OTV Trajectories. Advances in the Astronautical Sciences. 1999, 87(2):941-958

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Modern optimization
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[7] B. Dachwald. Optimization of interplanetary solar sailcraft trajectories using evolutionary neurocontrol. Journal of Guidance, Control, and Dynamics. 2004, 27(1):66-72
[8] Pini Gurfil, N. Jeremy Kasdin. Evolutionary Search for Deep-Space Science Mission Orbits. Journal of Guidance, Control, and Dynamics. 2006, 29(2):332-341
[9] B. Dachwald. Low-Thrust Trajectory Optimization and Interplanetary Mission Analysis Using Evolutionary Neurocontrol. Doctoral Thesis, University of the Federal Armed Forces Munich, Germany, 2004

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Other methods
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[10] A. E. Petropoulos. Refinements to the Q-law for low-thrust orbit transfers. Advances in the Astronautical Sciences. 2005, 120(1):963-982

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Threebody & Low-thrust
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[11] T.F. Starchville, Jr. R.G. Melton. Optimal Low-Thrust Transfers to Halo Orbits About the L2 Libration Point in the Earth-Moon System. AAS 98-205 paper,  1998 AAS/AIAA Space Flight Mechanics Conference.
[12] A. Sukhanov, N. Eismont. Low Thrust Transfer to Sun-Earth L1 and L2 Points with a Constraint on the Thrust Direction. LIBRATION POINT ORBITS AND APPLICATIONS. 10-14 June, 2002