The Minimum Manhattan Network Problem: Approximations and Exact Solutions. Benkert, M., Wolff, A., Widmann, F., & Shirabe, T. Computational Geometry Theory and Applications, 2006.
bibtex   
@article{TUW-120467,
    author = {Benkert, Marc and Wolff, Alexander and Widmann, Florian and Shirabe, Takeshi},
    title = {The Minimum Manhattan Network Problem: Approximations and Exact Solutions},
    journal = {Computational Geometry Theory and Applications},
    year = {2006},
    volume = {http://www.sciencedirect.com/science/journal/09257721},
    number = {35},
    numpages = {20}
}

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