V. A. Kim, “Sharp Lebesgue constants for interpolatory $\mathcal L$-splines of a formally self-adjoint differential operator”, Trudy Inst. Mat. i Mekh. UrO RAN, 17:3 (2011), 169–177
V. A. Kim, “Exact Lebesgue Constants for Interpolatory $\mathscr L$-Splines of Third Order”, Mat. Zametki, 84:1 (2008), 59–68; Math. Notes, 84:1 (2008), 55–63