List of Publications

S. Topalova, S. Zhelezova. Deficiency One Parallelisms of PG(5,2). Mathematics 2026, 14 (4), 687, MDPI, ISSN:2227-7390, DOI:10.3390/math14040687, SJR (Scopus):0.498, JCR-IF (Web of Science):2.2.

Tsvetanova, A., S. Zhelezova. On the structure of cyclic STS(v) of small order. Mathematics and Education in Mathematics, ЧСУ „Питагор“, София, 2026, ISSN:2815-4002.

S. Topalova, S. Zhelezova. The Cyclically Resolvable Steiner Triple Systems of Order 57. Mathematics 2025, 13, 212.

S. Topalova, S. Zhelezova. Point-cyclic KTS(45). In: Lilkova, E., Datcheva, M., Aleksandrova, T. (eds) Advanced Computing in Industrial Mathematics. BGSIAM 2023. Studies in Computational Intelligence, 1219, Springer, Cham, 2025, ISSN:1860-9503, DOI:10.1007/978-3-031-96311-7_22, SJR (Scopus):0.189.

S. Topalova, S. Zhelezova. Parallelisms of PG(3,4) with a Great Number of Regular Spreads. Large-Scale Scientific Computing, I. Lirkov, S. Margenov eds., LNCS, 13952, Springer, 2024, ISBN:978-3-031-56208-2, ISSN:03029743, 16113349, SJR (Scopus):0.606.

A. Betten, S. Topalova, S. Zhelezova. On parallelisms of PG(3,4) with automorphisms of order 2. Information and Computation, 301, art. 105201, Elsevier Inc., 2024, ISSN:0890-5401, SJR (Scopus):0.57, JCR-IF (Web of Science):0.8.

A. Tsvetanova, S. Zhelezova. Sorting in construction of resolutions of combinatorial designs. Mathematics and Education in Mathematics, 53, (Apr. 2024), 57 – 64.

S. Topalova, S. Zhelezova. Transitive Deficiency One Parallelisms of PG(3,7). Mathematics, 2023; 11 (11): 2458. SJR (Scopus):0.446, JCR-IF (Web of Science):2.4 Q1.

A. Betten, S. Topalova, S. Zhelezova. Parallelisms of PG(3,4) invariant under an elementary abelian group of order 4. Applicable Algebra in Engineering, Communication and Computing 33, Springer, ISSN: 1432-0622, 2022, 649 – 674. SJR (Scopus):0.470, Q3.

S. Topalova, S. Zhelezova. Parallelisms of PG(n,q). Mathematics and Education in Mathematics, 51, 2022, 113–123.

S. Topalova, S. Zhelezova. Backtrack search for parallelisms of projective spaces. In: P. Flocchini, L. Moura (Eds.), Combinatorial Algorithms IWOCA 2021. LNCS 12757, Springer, ISBN: 978-3-030-79987-8, 2021, 544-557. SJR (Scopus):0.407, Q2.

S. Topalova, S. Zhelezova. Parallelisms of PG(3,5) with an automorphism group of order 25. In: Extended Abstracts EuroComb 2021, J. Nešetřil, G. Perarnau, J. Ruι, O. Serra (Eds.) Trends in Mathematics, 14, Springer Birkhδuser, ISBN: 978-3-030-83823-2, 2021, 668-674. SJR (Scopus):0.217, Q4.

S. Topalova, S. Zhelezova. New Parallelisms of PG(3,5) with Automorphisms of Order 8. In: F. Boulier, M. England, T.M. Sadykov, E.V. Vorozhtsov (Ed.) Computer Algebra in Scientific Computing, 23rd International Workshop, CASC 2021, Sochi, Russia, September 13–17, 2021, LNCS 12865, Springer, Cham, ISBN: 978-3-030-85164-4, 2021, 409-419. SJR (Scopus):0.407, Q2.

S. Topalova, S. Zhelezova. On parallelisms of PG(5,2) invariant under a cyclic subgroup of order 21. XVII International Symposium "Problems of Redundancy in Information and Control Systems" (REDUNDANCY), 25-29 October 2021, Moscow, Russian Federation, IEEE Xplore, ISSN: 2694-5215, 2021, 97-100.

A. Betten, S. Topalova, S. Zhelezova. New Uniform Subregular Parallelisms of PG(3,4) Invariant Under an Automorphism of Order 2. Cybernetics and Information Technologies, 20, 6, Institute of Information and Communication Technologies - BAS, 2020, ISSN:1314-4081, DOI: 10.2478/cait-2020-0057, 18-27. SJR (Scopus):0.27, Q2.

S. Topalova, S. Zhelezova. Isomorphism and Invariants of Parallelisms of Projective Spaces. LNCS 12097, Springer, Cham, 2020, ISSN:03029743, 16113349, DOI:10.1007/978-3-030-52200-1_16, 162-172. SJR (Scopus):0.249, Q3.

S. Topalova, S. Zhelezova. Some parallelisms of PG(3,5) involving a definite type of spread, 2020 Algebraic and Combinatorial Coding Theory (ACCT), 2020, pp. 1-5, DOI: 10.1109/ACCT51235.2020.9383404 (IEEExplore, Scopus)

S. Zhelezova. On the extension of a partial solution of d spreads to a parallelism, Mathematics and Education in Mathematics, 2020, 173 – 177. ISSN:1313-3330.

A. Betten, S. Topalova, S. Zhelezova. Parallelisms of PG(3,4) invariant under cyclic groups of order 4. In: Ćirić M., Droste M., Pin JΙ. (eds) Algebraic Informatics. CAI 2019. Lecture Notes in Computer Science, 11545, Springer, Cham, 2019, ISBN:978-3-030-21362-6, DOI: https://doi.org/10.1007/978-3-030-21363-3_8, 88-99. SJR (Scopus): 0.427, Q2.

S. Topalova, S. Zhelezova. Types of spreads and duality of the parallelisms of PG(3,5) with automorphisms of order 13, Designs Codes and Cryptography, 2-3, 2019, DOI: 10.1007/s10623-018-0558-2. SJR (Scopus):0.549, JCR-IF (Web of Science):1.114, Q1.

S. Zhelezova. A method for constructing splitting (v,u x c, lambda) BIBDs. Cybernetics and Information Technologies, Institute of Information and Communication Technologies – BAS 18 (5), 2018, 87 – 94. ISSN:1311-9702, SJR (Scopus): 0.215, Q3.

A. Betten, S. Topalova and S. Zhelezova. Parallelisms of PG(3,4) invariant under a Baer involution. Proc. of the Sixteenth International Workshop on Algebraic and Combinatorial Coding Theory, Svetlogorsk (Kaliningrad region), Russia, 2018, 57 – 61.

S. Topalova, S. Zhelezova. New parallelisms of PG(3,4), Electronic Notes in Discrete Mathematics 57, Elsevier B.V., 2017, 193 – 198. ISSN:1571-0653, DOI:10.1016/j.endm.2017.02.032, SJR:0.262, Q3 (Scopus)

S. Zhelezova. A method for constructing splitting (v, u x c, l) BIBDs. Proc. of the Eighth International Workshop on Optimal Codes and Related Topics, July 10-14, Sofla, Bulgaria, 2017, 134 – 141.

S. Topalova, S. Zhelezova. New regular parallelisms of PG(3,5). Journal of Combinatorial Designs, 24 (10), 2016, 473 – 482. ISSN:1520-6610, SJR:0.821, ISI IF:0.657, Q2 (Scopus)

S. Zhelezova. On regular parallelisms of PG(3,5) with automorphisms of order 5, Science. Business. Society, 1 (6), 2016, 3 – 5.

S. Topalova and S. Zhelezova. Parallelisms of PG(3,4) with automorphisms of order 3, Proc. of the Fifteenth International Workshop on Algebraic and Combinatorial Coding Theory, Albena, Bulgaria, 2016, 272 – 277.

S. Zhelezova, On regular partial parallelisms of PG(3,7) with automorphisms of order 5. Сборник Юбилейна конференция „25 години ВТУ“, 2016

S. Topalova, S. Zhelezova. On point-transitive and transitive deficiency one parallelisms of PG(3,4), Designs, Codes and Cryptography, 75 (1), 2015, 9 – 19. DOI 10.1007/s10623-013-9887-3. ISSN 0925-1022, SJR: 0.564, IF 0.730

A. Avdzhieva, T. Balabanov, G. Evtimov, D. Kirova, H. Kostadinov, T. Tsachev, S. Zhelezova, N. Zlateva. Optimal Cutting Problem. 113-th Еuropean Study Group with Industry, Problems and Final Reports, 2015, 49 – 61.

S. Zhelezova, On point-cyclic parallelisms of PG(3,7). Mathematics and Education in Mathematics, 2015, 101 – 105. ISSN:1313-3330.

S. Topalova, S. Zhelezova. Doubly resolvable designs with small parameters, Ars Combinatoria 117, 2014, 289 – 302. ISSN: 0381-7032, SJR: 0.299, IF 0.204, Q3 (Scopus)

Ts. Baicheva, D. Bikov, Y. Borissov, L. Lazarova, A. Stojanova, L. Stoykova, S. Zhelezova, Finding an effective metric used for bijective S-Box generation by genetic algorithms. 104-th Еuropean Study Group with Industry, Problems and Final Reports, 2014, 71-76. ISBN 978-954-9526-87-5.

S. Topalova, S. Zhelezova. On transitive parallelisms of PG(3,4), Applicable Algebra in Engineering, Communication and Computing 24, (3-4), 2013, 159 – 164. ISSN 1432-0622, SJR: 0.462, IF 0.561, Q3 (Scopus)

S. Topalova, S. Zhelezova. Orthogonal resolutions and latin squares, Serdica Journal of Computing, 7 (1), 2013, 13-24. ISSN: 1312-6555.

S. Topalova, S. Zhelezova, Parallelisms of PG(3,5) with automorphisms of order 13,  Proc. VII Intern.Workshop Optimal Codes and Related Topics (OC), Albena, Bulgaria, 2013, 176-180.

N. Daskalova, P. Mateev, S. Zhelezova, Compressed representation of a partially defined integer function over multiple arguments. 95-th Еuropean Study Group with Industry, Problems and Final Reports, 2013, 29-32. ISBN 978-954-9526-84-4.

S. Topalova, S. Zhelezova, Parallelisms of PG(3,4) with automorphisms of order 5, Proc. of the International Workshop on Algebraic and Combinatorial Coding Theory, Pomorie, Bulgaria, 2012, 311 – 316. ISSN 1313-423X.

S. Zhelezova, A method for classification of doubly resolvable designs and its application. Serdica Journal of Computing, 5, 2011, 273–308. ISSN 1312-6555.

S.Zhelezova, The nonexistence of transitive 2-parallelisms of PG(5,3), Proc. of Annual Workshop on Coding Theory and Applications, Университетско издателство “Васил Априлов“ – Габрово, 2011, 39-41. ISSN 1314-5134.

S. Topalova, S. Zhelezova. Transitive and orthogonal 2-parallelisms of PG(5,2) with automorphisms of order 31, Graphs and Combinatorics 26 (5), 2010, 727 - 735. ISSN 1435-5914, SJR:0.729, IF:0.242, Q2 (Scopus)

S.Zhelezova. Cyclic parallelisms of PG(5,2), Mathematica Balkanica 24 (1-2), 2010, 141 - 146. ISSN 0205-3217.

S. Topalova, S. Zhelezova, Parallelisms of PG(3,4) with automorphisms of order 7,  Proc. of the International Workshop Optimal Codes and Related Topics, Varna, Bulgaria, 2009, 184-188. ISSN 1313-1117.

S. Topalova, S. Zhelezova, Classification of doubly resolvable designs and orthogonal resolutions, Enhancing Cryptographic Primitives with Techniques from Error Correcting codes, in NATO Science for Peace and Security Series - D: Information and Communication Security, vol. 23, B.Preneel, S.Dodunekov, V. Rijmen, S. Nikova eds., IOS Press, Amsterdam, 2009, 260-264. ISBN 978-1-60750-002-5.

S. Topalova, S. Zhelezova. On an algorithm for a double resolvability test, Acta Universitatis Apulensis 15, 2008, 323-330. ISSN 1582-5329.

S.Zhelezova. Parallel class intersection matrices of orthogonal resolutions, Serdica Journal of Computing, 2 (4) 2008, 321-330. ISSN 1312-6555.

S. Topalova, S. Zhelezova, Classification of the 2-spreads of PG(5,2), Mathematics and Education in Mathematics, 2008, 163-169. ISSN 1313-3330.

S. Topalova, S. Zhelezova, Sets of mutually orthogonal resolutions of BIBDs, Proc. XI Intern. Workshop on Algebraic and Combinatorial Coding Theory, Pamporovo, Bulgaria, 2008, 280-285. ISSN 1313-423X.

S.Zhelezova, PCIMs in constructing doubly resolvable designs, Proc. V Intern. Workshop OC, White Lagoon, Bulgaria, 2007, 260-266. ISBN:954-8986-18-3.

S. Topalova, S. Zhelezova, On the structure of doubly-resolvable 2-(21,3,1) designs, Proc. of X Intern. Workshop Algebraic and Combinatorial Coding Theory, Zvenigorod, Russia, 2006, 263-268.

S. Topalova, S. Zhelezova, On the classification of doubly resolvable designs, Proc. IV Intern.Workshop Optimal Codes and Related Topics (OC), Pamporovo, Bulgaria, 2005, 265-268, ISBN:954-8986-18-3.