Chvatal, V.Hoàng, C. T.Mahadev, N. V. R.de Werra, D.2006-08-162006-08-162006-08-16198710.1002/jgt.3190110405https://infoscience.epfl.ch/handle/20.500.14299/232971Four classes of perfectly orderable graphstext::journal::journal article::research article