Volume 14, Issue 4 Guangqing Wang Jinhui Li Some necessary and sufficient conditions for a VMO function Downloads Abstract PDF Full article PDF DOI { copied = true; setTimeout(() => copied = false, 2000) })" :aria-label="copied ? 'DOI copied' : 'Copy DOI'" :title="copied ? 'Copied' : 'Copy DOI'" > Find all available articles from these authors Guangqing Wang Jinhui Li Find more articles with the same keywords characterization commutator VMO Find more articles with the same subject classes 42B35 47B47