1. M. Anderson, Calc. Var. 5, (1997)#
2. A. Beilinson and V. Drinfeld, Chiral Algebras, (Amer
ican Mathematical Society Colloquium Publications,
vol. 51, Providence, R.I., 2004)#
3. D. Ben-Zvi, E. Frenkel, Vertex algebras and algebraic
curves, (Second Ed. Providence, Rhode Island: Ameri
can Mathematical Society, 2004)#
4. D. Conti, F. Rossi„ J. . Pure and Appl. Algebra, 223,
(2019)#
5. C. LeBrun, Math. Res. Lett. 3, (1996)#
6. J. Morgan, G. Tian, Clay math. Monograph 3, (2007)#
7. A. Sambusetti, An obstruction to the existence of
Einstein metrics on 4-manifolds, (C. R. Acad. Sci. Paris,
322, 1996)#
8. J. Park, J. Shin, H. Seok Yang, Phys. Rev. D 105,
(2022)#