J. Jankiewicz, A. A. . Gunes, O. Gunes, and P. Garsztka, “Informal Earnings and Domestic Production - the size of the shadow economy of the household. Case of Turkey”, REF, vol. 9, no. 2, pp. 117–142, Dec. 2025, doi: 10.18559/ref.2025.2.2770.