1. I.G. Avramidi, The Heat kernel approach for calculating the effective action in quantum field theory and quantum gravity, hep-th/9509077 [INSPIRE].
2. I.G. Avramidi, Heat kernel approach in quantum field theory, Nucl. Phys. B Proc. Suppl. 104 (2002) 3 [math-ph/0107018] [INSPIRE].
3. I.G. Avramidi, Covariant methods for the calculation of the effective action in quantum field theory and investigation of higher derivative quantum gravity, hep-th/9510140 [INSPIRE].
4. H.P. McKean and I.M. Singer, Curvature and eigenvalues of the Laplacian, J. Diff. Geom. 1 (1967) 43 [INSPIRE].
5. I.G. Avramidi, The Covariant Technique for Calculation of One Loop Effective Action, Nucl. Phys. B 355 (1991) 712 [Erratum ibid. 509 (1998) 557] [INSPIRE].