[8] C. Darwin, Proc. Roy. Soc. (London), A118 , 654 (1928). 

[9] H. A. Bethe and E. E. Salpeter, Quantum Mechanics of One- and Two-Electron Atoms (Springer, Berlin, 1957), Sec. 14. 

[10] See, e.g., C. K. Au and G. W. Rogers, Phys. Rev. A 22 , 1820 (1980). It was on finding this paper that we were reminded of the coupled first-order radial Dirac equations. 

[11] See, e.g., Muonic Atoms and Molecules , ed. by L. A. Schaller and C. Petitjean (Birkhauser, Basel, 1993). 

[12] J. D. Bjorken and S. D. Drell, Relativistic Quantum Mechanics , (McGraw-Hill, New York, 1964), p. 55. 

[13] T. Goldman and R. R. Silbar, Phys. Rev. C 77 , 865203 (2008). 

[14] M. Paris, Phys. Rev. C 68 , 025201(2003). 

[15] A. Soares de Castro and J. Franklin, Int. J. Mod. Phys. A 15 , 4355 (2000) 

[16] For the case when r 0 = 0, see C. L. Critchfield, Phys. Rev. D 12 , 923 (1975). 

[17] This interaction energy between two different quarks often goes by the name “color magnetic interaction,” which is essentially a hyperfine-like matrix element involving the coupling be- tween the two quark’s spins. T. Goldman and R. R. Silbar, talk at the April APS Meeting, 2008, Denver CO. 

[18] E.g., George E. Forsythe, Michael A. Malcolm, and Cleve B. Moler. Computer Methods for Mathematical Computations , (Englewood Cliffs, NJ: Prentice-Hall, 1977). See Chapter 6. 

[19] Mathematica is a software product of Wolfram Research, http:\\www.wolfram.com , and its use is described by S. Wolfram in The Mathematica Book , 4th ed. (Cambridge University Press, Cambridge, 1999). 

[20] http://t16web.lanl.gov/Silbar/ . 

[21] In more usual units, ¯ hc = 0.19732 GeV-fm, which can be used for converting from 1/fm to GeV. 

[22] T. Goldman and R. R. Silbar, “ Q ¯ q Mesons in a Relativistic Model”, in preparation. 

[23] B. D. Serot and J. D. Walecka, Advances in Nuclear Physics , ed. by J. W. Negele and E. Vogt (Plenum, New York, 1986), Vol. 16, p. 1. 

[24] N. Isgur, Phys. Rev. D 62 . 054026 (2000); Phys. Rev. D 62 . 014025 (2000). 

[25] P. R. Page, T. Goldman, and J. N. Ginocchio, Phys. Rev. Lett. 86 , 204 (2001). 

[26] C. Amsler et al. (Particle Data Group), Phys. Lett. B667 , 586 (2008). 

