@article {MR2441684,
	title = {Singular difference equations: an overview},
	journal = {Vietnam J. Math.},
	volume = {35},
	number = {4},
	year = {2007},
	pages = {339{\textendash}372},
	issn = {0866-7179},
	author = {Pham Ky Anh and Nguyen Huu Du and Le Cong Loi}
}
