期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1977
卷号：74
期号：6
页码：2211-2213
DOI：10.1073/pnas.74.6.2211
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：A technique is introduced to relate differentiation and covering properties of a basis. In particular, we find that the basis associated with a sparse set of directions differentiates integrals of functions locally in L2.
关键词：covering property V 2 ; sparse set of directions ; Busemann-Feller basis
