1. P. KOSKELA, Z. ZHU, Product of extension domains is still an extension domain, Indiana Univ. Math. J. 69 (2020), no. 1, 137–150.
2. T. IWANIEC, J. ONNINEN, Z. ZHU, Deformations of Bi-conformal Energy and a new Characterization of Quasiconformality, Arch. Ration. Mech. Anal. 236 (2020), no. 3, 1709–1737.
3. T. IWANIEC, J. ONNINEN, Z. ZHU, Creating and Flattening Cusp Singularities by Deformations of Bi-conformal Energy, J. Geom. Anal. 31 (2021), no. 3, 2331-2353.
4. S. ERIKSSON-BIQUE, P. KOSKELA, J. MALÝ, Z. ZHU, Pointwise inequalities for Sobolev functions on outward cuspidal domains, Int. Math. Res. Not. IMRN no. 5, 3748–3759..
5. T. IWANIEC, J. ONNINEN, Z. ZHU, Singularities in 
-quasidisks, Ann. Fenn. Math. 46 (2021), no. 2, 1053–1069.
6. Z. ZHU, Sobolev extension on quasidisks, Potential Anal (2021). https://doi.org/10.1007/s11118-021-09948-7
7. M. GARCÍA-BRAVO, T. RAJALA, Z. ZHU, Bi-Lipschitz invariance of planar BV – and 
-extension domains, Proc. Amer. Math. Soc. 150 (2022), no. 6, 2535–2543.
8. Z. ZHU, Pointwise inequalities for Sobolev functions on generalized cuspidal domains, Ann. Fenn. Math. 47 (2022), no. 2, 747–757.
9. P. KOSKELA, A. UKHLOV, Z. ZHU, The volume of the boundary of a Sobolev (p, q)-extension domain, J. Funct. Anal. 283 (2022), no. 12, Paper No. 109703.
10. P. KOSKELA, Z. ZHU, Sobolev extension via reflections, accepted by J. Math. Sci.(N.Y.).
