@Article{zbMATH03364079,
Author = {Stephen J. {Greenfield}},
Title = {{Hypoelliptic vector fields and continued fractions}},
FJournal = {{Proceedings of the American Mathematical Society}},
Journal = {{Proc. Am. Math. Soc.}},
ISSN = {0002-9939},
Volume = {31},
Pages = {115--118},
Year = {1972},
Publisher = {American Mathematical Society (AMS), Providence, RI},
Language = {English},
DOI = {10.2307/2038524},
MSC2010 = {35H10},
Zbl = {0229.35024}
}