1. Acerbi, E., Fusco, N.: A approximation lemma for $$W^{1,p}$$ functions. In: Ball, J.M. (ed.) Proceedings of the Symposium on Material Instabilities and Continuum Mech, pp. 1–5. Oxford Science Publications, Oxford (1988)
2. Adams, R.A., Fournier, J.J.F.: Sobolev Spaces Pure and Applied Mathematics (Amsterdam), vol. 140, 2nd edn. Elsevier, Amsterdam (2003)
3. Barden, D.: Simply connected five-manifolds. Ann. Math. 82, 365–385 (1965)
4. Besov, O.V., Il’in, V.P., Nikol’skiĭ, S.M.: Integral representations of functions and imbedding theorems. In: Taibleson, M.H., V. H. Winston & Sons (eds.) Scripta Series in Mathematics, vol. II. Halsted Press, Washington (1979)
5. Bonk, M., Heinonen, J.: Quasiregular mappings and cohomology. Acta Math. 186, 219–238 (2001)