C. Pacheco, M. A. Duarte-Mermoud, N. Aguila-Camacho, and R. Castro-Linares, “Fractional-order State Observers for Integer-order Linear Systems”, JAND, vol. 6, no. 2, pp. 251–264, Aug. 2026, doi: 10.5890/JAND.2017.06.010.