Null-A Three, usually written Ā Three, is a 1985 science fiction novel by Canadian-American writer A. E. van Vogt. It incorporates concepts from the General semantics of Alfred Korzybski and refers to

The World of Null-A, sometimes written The World of Ā, is a 1948 science fiction novel by Canadian-American writer A. E. van Vogt. It was originally published as a three-part serial in 1945 in Astound