Kirov, N., Dozov, I., Jordanova, J., Hadjichristov, G. B., Fontana, M. P.. Uncorrelated jumps model for molecular orientational relaxation in liquid crystals. Journal of Molecular Structure, 839, 1-3, Elsevier, 2007

N. Kirov, I. Dozov, J. Jordanova, G. Hadjichristov, Uncorrelated jumps model for orientational rrelaxation in liquid crystals - nanosecond and picosecond time domains, Proceedongs of the 14the International School of Condensed Matter Physics, 17-22 September 2006, Varna, Bulgaria, Part 2, p. 60-64

Hamelmann F., Heinzmann U., Szekeres A., Kirov N., Nikolova T. Deposition of silicon oxide thin films in TEOS with addition of oxygen to the plasma ambient: IR spectra analysis. Journal of optoelectronics and advanced materials, 7, 1, 2005

N. Kirov, G. Hadjichristov, Nonlinear optics in materials: integral transformation of optical four-wave mixing spectra, Proceedings of 12 ISCMP (2002) p. 725-728

P. Simova, N. Kirov, M. Fontana, H. Ratajczak, Atlas of Vibrational Spectra of Liquid Crystals, World Scientific, Singapore, 1988

N. Kirov, P. Simova, Vibrational Spectroscopy of Liquid Crystals, Sofia, BAS, 1984, 329 s

N. Kirov, M. Fontana, F. Cavatorta, Spectroscopic and thermodynamic Investigations of the Polymorphism of the solid state of Liquid crystals, Journal of Molecular Structure, v. 59, pp. 147-160 (1980)

N. Kirov, M. Fontana, F. Cavatorta, Raman, Infrared and Calorimetric Investigations of the Unstable Modifications Formed by Fast Cooling of the Mesophase, Molecular Crystals and Liquid Crystals, v. 54, pp. 207-220 (1979)

N. Kirov, F. Savatorta, Raman, Infrared and Calorimetric Investigations of Solid Phases formed by 4-Nitrophenyl 4-n-Octyloxy-Benzoate, Spectroscopy Letters, 11(8) 589-605 (1978)

F. Cavatorta, M. Fontana, N. Kirov, Raman and Calorimetric investigations of fast quenched 4-nitrophenyl, 4-octyloxybenzoate, Forschungen Uber Flussige Kristalle, Halle, 1978, 29-37

F. Cavatorta, M. Fontana, N. Kirov, Raman and Calorimetric evidences for the existence of three solid modifications in E B B A, Molecular Crystals and Liquid Crystals, v. 34, pp. 241-248 (1977)

E. Keskinova, W. Wrnke, N. Kirov, P. Kircheva, Spectra of Intranolecular Vibrations of Methyl Thionine Chloride (Methylene Blue), Болг. Физ. Журнал, т. 6, кн. 3, с. 370-374 (1979)

N. Kirov, P. Simova, H. Ratajczac, Influence of a.c. Electric Field on IR Spectra of some nematic Liquid Crystals with Positive and Negative Dielectric Anisotropy, Journal of Molecular Structure, v. 46, pp. 487-493 (1878)

P. Simova, N. Kirov, Determination of Elastic Constant K33 for Some Nematic Liqued Crystals with Strong Positive Dielectric Anisotropy by MNeans of IR Absorption Spectroscopy, Molecular Crystals and Liquid Crystals, v. 46, pp. 137-145 (1978)

N. Kirov, P. Simova, S. Sainov, Broadening of IR Absorption Bands of p-Methoxybenzylidene, p, n-Butilaniline (MBBA) under the influence of an A. C. Electric Field, Spectroscopy Letters, 10(10) 783-789 (1977)

P. Simova, M. Petrov, N. Kirov, Coherent Light Diffraction in a Smectic C Liquid Crystal, Molecular Crystals and Liquid Crystals, Gordon and Breach Science Publishers Ltd, Printed in Holland, v. 42, pp. 295-305 (1977)

N. Kirov, P. Simova, M. Sabeva, Depolarization of Light Scattered in Nematic Liquid Crystals, Molecular Crystals and Liquid Crystals, v. 33, pp. 189-194 (1976)

P. Simova, N. Kirov, Anizotropy of Rotational Diffusion in Nematic and Isotropic Phases, Spectroscopy Letters, 7(2) 55-61 (1974)

N. Kirov, P. Simova, Infrared Absorption Spectra of Liquid Crystals, Molecular Crystals and Liquid Crystals, v. 30, pp. 59-71 (1975)

P. Simova, N. Kirov, Infrared Spectra of Liquid Crystals - III Rotational Diffusion in Smectic and Cholesteric Mesophase, Spectroscopy Letters, 8(8) 561-570 (1975)

P. Simova, N. Kirov, Rotational Diffusion of Nonassociated Molecules in Pure Liquids and in Dilute Solutions, Българки физически журнал, т. 1, кн. 1, с. 21-30, 1974

N. Kirov, P. Simova, On the Temperature dependence of IR Integral Intensity in Crystal, Nematic and Isotropic P-Azoxyanisole (PAA), Доклады БАН, т. 26, № 8, с. 1013-1015, 1973

P. Simova, N. Kirov, IR Absorption Spectra of Liquid Crystals, Advances in Molecular Relaxacions Processes, v. 5, pp. 233-243, 1973

N. Kirov, P. Simova, Infrared absorption spectra of liquid crystals - 1, Spectrochimica Acta, Pergamon Press, Printed in Northern Ireland, v. 29A, pp. 55-62, 1973

N. Kirov, P. Simova, The Potential Barriers of the PAA Molecules in Crystal Nematic and Isotropic Phases, Physics Letters, v. 37A, Nr. 1, 25 October 1971, p. 51-52