1. Shelekhov, A.M., Lazareva, V.B., Utkin, A.A. Curvilinear three-webs (Tvers. gos. univ., Tver, 2013) [in Russian].
2. Mandelbrot, B.B. The fractal geometry of nature (W. H. Freeman and Co., San Francisco, 1982).
3. Falconer, K. Fractal geometry: mathematical foundations and applications (John Wiley and Sons, New York, 1990).