1. Ambrosio, L., Kirchheim, B.: Rectifiable sets in metric and Banach spaces. Math. Ann. 318(3), 527–555 (2000)
2. Antonelli, G., Merlo, A.: On rectifiable measures in Carnot groups: structure theory. In: arXiv e-prints. arXiv:2009.13941 (2020)
3. Balogh, Z.M.: Size of characteristic sets and functions with prescribed gradient. J. Reine Angew. Math. 564, 63–83 (2003)
4. Bogachev, V.I.: Measure theory, vol. I, pp. xviii+500, vol. II, pp. xiv+575. Springer, Berlin (2007)
5. Capogna, L., Danielli, D., Pauls, S.D., Tyson, J.T.: An introduction to the Heisenberg group and the sub-Riemannian isoperimetric problem. Progress in Mathematics, vol. 259, pp. xvi+223. Birkhäuser Verlag, Basel (2007)