Ashyralyev, Allaberen, and Charyyar Ashyralyyev. “On the Problem of Determining the Parameter of an Elliptic Equation in a Banach Space”. Nonlinear Analysis: Modelling and Control, vol. 19, no. 3, Oct. 2014, pp. 350-66, https://doi.org/10.15388/NA.2014.3.3.