I have read a paper of Z. Shen [1]. In the paper the author mentioned we can deal with two-dimensional elliptic systems by adding a dummy variable (the method of ascending) and use the results on the related three-dimensional problem. I guess it is a standard way to deal with elliptic systems with lower dimensions. However, I do not find any reference about it: can you give me some references or hints?
Reference
[1] Zhongwei Shen, "Convergence rates and Hölder estimates in almost-periodic homogenization of elliptic systems" (English), Analysis & PDE 8, No. 7, 1565-1601 (2015), DOI: 10.2140/apde.2015.8.1541, MR3399132, Zbl 1327.35025.