1. Gediminas Gaigalas, Julius Kaniauskas and Zenonas Rudzikas. Diagrammatic Technique of the Angular Momentum Theory and Second Quantization // Lietuvos Fizikos Rinkinys (English translation - Soviet Physics Collection, 1985, Vol. 25, p. 1-9), 1985, Vol. 25, p. 3-13.
2. Gintaras Merkelis, Gediminas Gaigalas and Zenonas Rudzikas. Irreducible Tensorial Form of the Effective Hamiltonian of an Atom and the Diagrammatic Representation in the First Two Orders of the Stationary Perturbation Theory // Lietuvos Fizikos Rinkinys (English translation - Soviet Physics Collection, 1985, Vol. 25, p. 10-22), 1985, Vol. 25, p. 14-31.
3. Gintaras Merkelis and Gediminas Gaigalas. Expressions for Reduced Matrix Elements of Non-Relativistic effective Hamilgtonian of Atom in the First Order of Stationary Perturbation Theory for Configurations with Two unifilled Shells n₁l₁^N' n₂l₂^N'' //  Spectroscopy of Autoionized States of Atoms and Ions (Moscow, Scientific Council of Spectroscopy, 1985), p. 20-42.
4. Gediminas Gaigalas. Diagrammatic Approach to Irreducible Tensorial Operators And Its Application to Perturbation Theory // Spectroscopy of Autoionized States of Atoms and Ions (Moscow, Scientific Council of Spectroscopy, 1985), p. 43-61.
5. Gintaras Merkelis, Gediminas Gaigalas, Julius Kaniauslas and Zenonas Rudzikas. Application of the Graphical Method of the Angular Momentum Theory to the Study of the Stationary Perturbation Series // Izvestija AN SSSR, Ser. Fiz., 1986, Vol. 50, p. 1403-1410.
6. Gediminas Gaigalas and Gintaras Merkelis. Calculation Program of Submatrix Elements of Irreducible Tensor Products of the Creation and Destruction Operators // A Collection of Programs on Mathematical Supply of Atomic Calculations, Ed. 17 (Institute of Theoretical Physics of the Academy of Sciences of the Lithuanian SSR, 1986), p. 78-132.
7. Gediminas Gaigalas and Gintaras Merkelis. Application of the Method of Irreducible Tensorial Operators to Study the Expansion of Stationary Perturbation Theory // Acta Phys. Hungarica, 1987, Vol. 61, p. 111-114.
8. Gediminas Gaigalas and Gintaras Merkelis. Irreducible Tensorial Form of One Particle Operator // VINITI, Academy of Sciences of the Lithuanian SSR, YDK 539.18+530.145, 1988, p. 1-32.
9. Gintaras Merkelis and Gediminas Gaigalas. The Graphical Method of Construction and the Calculation of Spin-Angular Parts of Operator's Expansion for Many-Body Perturbation Theory for Atoms with Several Open Shells // Energy Levels and Transition Probabilities in Atoms and Ions (Moscow scientific Council of Spectroscopy, 1989), p. 4-63.
10. Marius-J. Vilkas, Gediminas Gaigalas and Gintaras Merkelis. Calculations of Electron-Electron Correlation Corrections for Energy Levels of Carbon Ioselectronic Sequence of Configurations 1s²2s²2p², 1s²2s2p³ and 1s²2s⁴ by Multireference MBPT // Lietuvos Fizikos Rinkinys, 1991, Vol. 31, p. 142-164.
11. Marius-J. Vilkas, Gediminas Gaigalas and Gintaras Merkelis. Calculation of Electron Correlations Using the Method of Quasi Degenerate Stationary Perturbation Theory for Levels of the Configurations 1s²2s²2p², 1s²2s2p³ and 1s²2s⁴ of Carbon Isoelectronic Sequence // Lithuanian Journal of Physics. ISSN 1392-1932. FISICA, 1991, Vol. 31, p. 84-97.
12. Gediminas Gaigalas, Julius Kaniauskas, Romas Kisielius, Gintaras Merkelis and Marius-J. Vilkas. Second-Order MBPT Results for Oxygen Isoelectronic Seguence // Physica Scripta, 1991, Vol. 49, p. 135-147.
13. Marius-J. Vilkas, Gintaras Merkelis, Romas Kisielius, Gediminas Gaigalas, Andrius Bernotas and Zenonas Rudzikas. Ab initio Calculation of E1 Transitions in the Oxygen Isoelectronic Sequence // Physica Scripta, 1994, Vol. 49, p. 592-600.
14. Gintaras Merkelis, Marius-J. Vilkas, Gediminas Gaigalas and Romas Kisielius. MBPT Calculation of Energy Spectra and E1 Transitions in the Boron Isoelectronic Sequence // Physica Scripta, 1995, Vol. 51, p. 233-251.
15. C. Froese Fischer, A. Ynnerman and Gediminas Gaigalas. Multiconfiguratio-Hartree-Fock Calculations for the Electron Affinity of Boron // Physical Review A, 1995, Vol. 51, p. 4611-4616.

Software

1. Gediminas Gaigalas and Gintaras Merkelis. Calculation Program of Submatrix Elements of Irreducible Tensor Products of the Creation and Destruction Operators // A Collection of Programs on Mathematical Supply of Atomic Calculations, Ed. 17 (Institute of Theoretical Physics of the Academy of Sciences of the Lithuanian SSR, 1986), p. 78-132.
2. Gediminas Gaigalas, Marius-J. Vilkas, Andrius Bernotas and Gintaras Merkelis. Program to Calculate Energy Spectra of Open-Shell by the MBPT Methods, XXIII EGAS Conference, Torun, Poland, 9-12 July 1991 (Editors: S. Lengowski and Z. Rudzikas).

Conferences Presentations

in English

1. Gediminas Gaigalas and Gintaras Merkelis. Application of the Method of Irreducible Tensorial Operators to Study the Expansion of Stationary Perturbation Theory, Conference of Spectroscopy Committees of Socialist Countries, Balatonszeplak-Felso, Hungary, 31 August - 5 September 1986 (poster).
2. Gedimnas Gaigalas, Gintaras Merkelis, Marius-J. Vilkas and Zenonas Rudzikas. Application of the Many-Body Perturbation Theory to the Calculation of the Energy Spectra of the Configurations 1s²2s²2p² and 1s²2s⁴, Third European Conference on Atomic and Molecular Physics, Bordeaux, France, 3-7 April 1989 (Editor: A. Salin).
3. Marius-J. Vilkas, Gediminas Gaigalas, Gintaras Merkelis and Zenonas Rudzikas. Application of Many-Body Perturbation Theory to the Investigation of Energy Spectra of Atoms and Ions with Open Shells, 3^rd International Colloquiuum on Atomic Spectra and Oscillator Strengths for Astrophysics and Fusion, Amsterdam, Netherlands, 28-31 August 1990 (Editor: J.E. Hansen).
4. Gintaras Merkelis, Gediminas Gaigalas and Marius-J. Vilkas. Multireference MBPT Calculation of Energy Levels Along the Carbon Sequance, XXII EGAS Conference, Uppsala, Sweden, 10-13 July 1990 (Editor: A. Wannstrom).
5. Gediminas Gaigalas, Marius-J. Vilkas, Andrius Bernotas and Gintaras Merkelis. Program to Calculate Energy Spectra of Open-Shell by the MBPT Methods, XXIII EGAS Conference, Torun, Poland, 9-12 July 1991 (Editors: S. Lengowski and Z. Rudzikas).
6. Gediminas Gaigalas, Romas Kisielius, Gintaras Merkelis and Marius-J. Vilkas. Second-Oder MBPT Results for Oxygen Isoelectronic Sequence, 4^th EPS Europhysics Conference, Ryga, Latvija, 6-10 April 1992 (Editor: K. Bethge).
7. Gediminas Gaigalas, Romas Kisielius, Gintaras Merkelis and Marius-J. Vilkas. Calculation of Energy Spectra and transition Probabilities for Magnesium Like Ions Using MBPT in the Complete Model Space, 4^th EPS Europhysics Conference, Ryga, Latvija, 6-10 April 1992 (Editor: K. Bethge).
8. Gediminas Gaigalas, Romas Kisielius, Gintaras Merkelis and Marius-J. Vilkas. E2 and M1 Transition Probabilities in Ions of the Nitrogen Isoelectronic Sequence Calculated Using MBPT, Symposium 155 Planetary Nebulae, Innsbruck, Austria, 13-17 July 1992.
9. Gediminas Gaigalas, Romas Kisielius, Gintaras Merkelis, Zenonas Rudzikas and Marius-J. Vilkas. MBPT Results for Dn=0 Electronic Dipole Transitions, Symposium 155 Planetary Nebulae, Innsbruck, Austria, 13-17 July 1992.
10. Marius-J. Vilkas,  Romas Kisielius, Gintaras Merkelis and Gediminas Gaigalas. Ab initio Estimation of the Correlation Correction for n=3 Complex Ions, XXV EGAS Conference, Caen, France, 13-16 July 1993 (Editor: K. Bethge).
11. Gintaras Merkelis, Marius-J. Vilkas, Gediminas Gaigalas and Romas Kisielius. Second Order MBPT Results for Boron and Fluorine Isoelectronic Sequence, XXV EGAS Conference, Caen, France, 13-16 July 1993 (Editor: K. Bethge).
12. Romas Kisielius, Gediminas Gaigalas, Gintaras Merkelis and Marius-J. Vilkas. Correlation Effects for Radiative Transitions in Carbon Isoelectronic Sequence, XXV EGAS Conference, Caen, France, 13-16 July 1993 (Editor: K. Bethge).
13. Gintaras Merkelis, Marius-J. Vilkas, Romas Kisielius and Gediminas Gaigalas. Second-Order MBPT Calculation of the Energy Spectra and E1 Transitions in Si-like Sequence, XXVI EGAS Conference, Barcelona, Spain, 12-15 July 1994 (Editor: R. Pick).
14. Zenonas Rudzikas, Gintaras Merkelis, Marius-J. Vilkas, Romas Kisielius and Gediminas Gaigalas. Theoretical Studies of Structure and Spectra of Complex Highly Charged Ions, 7^th International Conference on the Physics of Highly Charged Ions HCI-94, Vienna, Austria, 19-23 September 1994 (Editors: F. Aumayr and HP. Winter).
15. Gediminas Gaigalas, Zenonas Rudzikas and C. Froese Fischer. Efficient Methods for Angular Integrations in Large-Scale Atomic Structure Calculations, 5^th EPS Conference on Atomic and Molecular Physics, Edinburgh, UK, 3-7 April 1995 (Editor: R.C. Thompson).
16. Gintaras Merkelis, Marius-J. Vilkas, Romas Kisielius and Gediminas Gaigalas. Treatment of the Correlation Correction for the n=2 Complex Ions by Using the Second-Order Perturbation Theory with HF Orbital Bases Set, 5^th EPS Conference on Atomic and Molecular Physics, Edinburgh, UK, 3-7 April 1995 (Editor: R.C. Thompson).

in Russian

1. Gediminas Gaigalas, and Gintaras Merkelis. The Irreducible Tensorial Form of Effective Hamiltonian of an Atom in the First Two Orders, Conference on the Research in the Spectroscopy and Quantum Electronics, Vilnius, Lithuania SSR, 1983.
2. Gintaras Merkelis and Gediminas Gaigalas. The Irreducible Tensorial Form of Effective Hamiltonian for an Atom with Open Shells in Perturbation Theory, Conference on Theory of Atoms and Atomic Spectra, Minsk, Belarus SSR, 1983.
3. Gediminas Gaigalas. Graphical Technique for Examination of Vacuum Average in the Case of One Open Shell, Conference on the Research in the Spectroscopy and Quantum Electronics, Vilnius, Lithuania SSR, 28-29 May 1985.
4. Gediminas Gaigalas and Julius Kaniauskas. Grpahical Method for Study of Irreducible Tensorial Form of Effective Hamiltonian in Perturbation Theory, XI Conference on Theory of Atoms and Atomic Spectra, Uzgorod, Ukraine SSR, 24-26 September 1985.
5. Gintaras Merkelis, Gediminas Gaigalas and Zenonas Rudzikas. Determination of the Expressions for the Submatrix Elements of the Nonrelativistic Effective Hamiltonian of Atom in the First Two Orders of Perturbation Theory in the case of Configuration of Two Open Shells n₁l₁^N' n₂l₂^N'', XI Conference on Theory of Atoms and Atomic Spectra, Uzgorod, Ukraina SSR, 24-26 September 1985.
6. Gediminas Gaigalas. The Irreducible Tensorial Form of Effective Operator, Conference on the Research in the Spectroscopy and Quantum Electronics, Vilnius, Lithuania SSR, 25-28 May 1987.
7. Gintaras Merkelis, Gediminas Gaigalas and Marius-J. Vilkas. Study of Effective Hamiltonian of Atom with Open Shells in the Case of One- and Two- Particle Interaction, Conference on Theory of Atoms and Atomic Spectra, Tbilisi, Georgia SSR, 11-14 May 1988.
8. Gediminas Gaigalas. Calculation Energy Levels of the Configurations 1s²2s²2p² and 1s²2s⁴ of O III in the First Two Order of Perturbation Theory, IX Conference on the Research in the Spectroscopy and Quantum Electronics, Vilnius, Lithuania SSR, 23-25 May 1989.
9. Marius-J. Vilkas, Andrius Bernotas, Gediminas Gaigalas and Gintaras Merkelis. Calculations of Energy Levels of Carbon Ioselectronic Sequence by Many Body Perturbation Theory, Conference on Theory of Atoms and Atomic Spectra, Tomsk, Russia SSR, 1989.