E-print: http://arxiv.org/abs/1304.6819
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E-print: http://arxiv.org/abs/cond-mat/9801279
E-print: http://arxiv.org/abs/cond-mat/0403022
E-print: http://arxiv.org/abs/1204.0922
E-print: http://arxiv.org/PS_cache/arxiv/pdf/0905/0905.3096v1.pdf
E-print: https://arxiv.org/abs/1610.08818
E-print: http://arxiv.org/abs/cond-mat/9907297
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E-print: http://arxiv.org/abs/1105.1694
E-print: http://arxiv.org/abs/cond-mat/9906347
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E-print: https://ssrn.com/abstract=3070850