[1] Eggleton R B, Erdös P, Skilton D K. Colouring the real line [J]. J Comb Theory Ser B, 1985, 39: 86-100.
[2] Chang G J, Huang L, Zhu X. Circular chromatic numbers and fractional chromatic numbers of distance graphs [J]. Europ J Comb, 1998, 19:423-431.
[3] Voigt M, Walther H. On the chromatic numbers of special distance graphs [J]. Discrete Mathematics, 1991, 97:395-397.
[4] Eggleton R B, Erdös P, Skilton D K. Colouring prime distance graphs [J]. Graphs and Combinatorics, 1990, 6(1): 17-32.
[5] Viogt M, Walther H. Chromatic number of prime distance graphs [J]. Discrete Appl Math, 1994, 51: 197-209.
[6] Huang L, Chang G J. Circular chromatic numbers of distance graphs with distance sets missing multiples [J]. Europ J Comb, 2000, 21: 241-248.
[7] Liu D D F, Zhu X. Distance graphs with missing multiples in the distance sets [J]. J Graph Theory, 1999, 30: 245-259.
[8] Chang G, Liu D, Zhu X. Distance graphs and T-coloring [J]. J Comb Theory Ser B, 1999, 75: 259-269.
[9] Walther H. Über eine spezielle klasse unendlicher graphen [A]. In: Wagner K, Bodendiek R, eds. Graphentheorie [C]. Bibliographisches Institut, Mannhein, 1990.268-295.
[10] Voigt M. Die chromatische zahl einer speziellen klasse unendlicher graphen [D]. Ilmenau: Technical University, 1992.
[11] Margit Voigt. Colouring of distance graphs [J]. ARS Combinatoria, 1999, 52: 3-12.
[12] Kemnitz A, Kolberg H. Colouring of integer distance graphs [J]. Discrete Mathematics, 1998, 191: 113-123.
[13] Frobenius G. Über matrizen aus nichtngativen elementen [M]. Berlin: Sitzungsberichte Preuss Akad Wiss, 1912.456-477.
[14] Zhu X. Circular chromatic number: a survey [J]. Discrete Mathematics, 2001, 229: 371-410.