An exact result for (0,±1)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(0, \pm \, 1)$$\end{document}-vectors

After reviewing some memories and results of a dear friend and great collaborator, Michel-Marie Deza, a result (Theorem 8) is proven that could have very well been a joint paper, should not he have departed under tragical circumstances. This new result determines the maximum possible size of a family of (0,±1)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(0, \pm \, 1)$$\end{document}-vectors without three vectors adding up to the all-zero vector.