\alpha-Variation and Transformation into C^n Functions M. LaczkovichD. Preiss Indiana University Mathematics Journal 1985 text pdf 10.1512/iumj.1985.34.34024 10.1512/iumj.1985.34.34024 en Indiana Univ. Math. J. 34 (1985) 405 - 424 state-of-the-art mathematics http://iumj.org/access/