A. Bostan and M. Kauers, The complete generating function for Gessel's walk is algebraic, Proc. Amer, pp.3063-3078, 2010.

M. Bousquet-mélou and M. Mishna, Walks with small steps in the quarter plane, Contemp. Math, vol.520, pp.1-40, 2010.
DOI : 10.1090/conm/520/10252

G. Fayolle and R. Iasnogorodski, Two coupled processors: The reduction to a Riemann-Hilbert problem, Zeitschrift f???r Wahrscheinlichkeitstheorie und Verwandte Gebiete, vol.13, issue.No. 6, pp.325-351, 1979.
DOI : 10.1007/BF00535168

G. Fayolle, R. Iasnogorodski, and V. Malyshev, Random walks in the quarter plane, 1999.
URL : https://hal.archives-ouvertes.fr/inria-00572276

G. Fayolle, V. Malyshev, and M. Menshikov, Topic in the constructive theory of countable Markov chains, 1995.
DOI : 10.1017/CBO9780511984020

G. Fayolle and K. , On the holonomy or algebraicity of generating functions counting lattice walks in the quarter plane. Markov Process, pp.485-496, 2010.
URL : https://hal.archives-ouvertes.fr/hal-00559676

I. Kurkova and K. , Random walks in $(\mathbb{Z}_{+})^{2}$ with non-zero drift absorbed at the axes, Bulletin de la Société mathématique de France, vol.139, issue.3
DOI : 10.24033/bsmf.2611
URL : https://hal.archives-ouvertes.fr/hal-00696352

G. Litvinchuk, Solvability theory of boundary value problems and singular integral equations with shift, 2000.
DOI : 10.1007/978-94-011-4363-9

V. Malyshev, Positive random walks and Galois theory, Uspehi Mat. Nauk, vol.26, pp.227-228, 1971.

M. Mishna and A. Rechnitzer, Two non-holonomic lattice walks in the quarter plane, Theoretical Computer Science, vol.410, issue.38-40, pp.3616-3630, 2009.
DOI : 10.1016/j.tcs.2009.04.008

G. Springer, Introduction to Riemann Surfaces, 1981.