add arXiv reference

Author: MikaelSlevinsky

README.md

@@ -130,6 +130,6 @@ As with other fast transforms, `plan_sph2fourier` saves effort by caching the pr
 
    [4]  R. M. Slevinsky. <a href="https://doi.org/10.1093/imanum/drw070">On the use of Hahn's asymptotic formula and stabilized recurrence for a fast, simple, and stable Chebyshev—Jacobi transform</a>, in press at *IMA J. Numer. Anal.*, 2017.
 
-   [5]  R. M. Slevinsky. <a href="https://arxiv.org/abs/1705.05448">Fast and backward stable transforms between spherical harmonic expansions and bivariate Fourier series</a>, arXiv, 2017.
+   [5]  R. M. Slevinsky. <a href="https://arxiv.org/abs/1705.05448">Fast and backward stable transforms between spherical harmonic expansions and bivariate Fourier series</a>, arXiv:1705.05448, 2017.
 
    [6]  A. Townsend, M. Webb, and S. Olver. <a href="https://doi.org/10.1090/mcom/3277">Fast polynomial transforms based on Toeplitz and Hankel matrices</a>, in press at *Math. Comp.*, 2017.