S. G. Kim and C. Y. Lee, “Smooth bilinear forms of ${\mathcal L}(^2\mathbb{R}_{h(w_1, w_2)}^2)$ and ${\mathcal L}(^2\mathbb{R}_{h^{’}(w_1, w_2)}^2)$”, MFAT, vol. 29, no. 1-2, pp. 39–56, Mar. 2023, doi: https://doi.org/10.31392/MFAT-npu26_1--2.2023.04.