Akpan D., “Singularities of two-dimensional Nijenhuis operators”,
European Journal of Mathematics, 2022, vol 8, 1328-1340. DOI https://doi.org/10.1007/s40879-022-00585-x
Akpan D., “Almost differentially nondegenerate Nijenhuis operators”,
Russian Journal of Mathematical Physics, 2023, vol 29, 413-416. DOI https://doi.org/10.1134/S106192082204001X
Akpan D., “Elementary differential singularities of three-dimensional Nijenhuis operators”,
Russian Journal of Mathematical Physics 2023, vol 30, 425-431, (with A. Oshemkov). DOI https://doi.org/10.1134/S1061920823040015
Akpan D., “Phases of semiclassical solutions of the two-dimensional massless Dirac equation with a constant electromagnetic field” Chebyshevskii Sbornik. 2025;26(4):475-486 (with I. Bogaevskii, N.Ziatdinov, A.Oshemkov). DOI https://doi.org/10.22405/2226-8383-2025-26-4-475-486
Akpan D., “Beltrami problem in dimension two: local normal forms”, on print (with A. Bolsinov)