There are numerous examples where PIE "*o" appears to result in Latin "a" instead of expected "o", mostly next to labial or labializing consonants. A group of cases showing "*-ow-" > "*-aw-" > "-av-" (before stress), "*-ōw-" > "*-āw-" > "-āv-" is known as Thurneysen-Havet's law: examples include PIE "*lowh₃ṓ" > "*lawō" > "lavō" 'I wash'; PIE "*oḱtṓwos" > "*oktāwos" > "octāvus" 'eighth' (but "octō" 'eight'). Other cases remain more disputed, such as "mare" 'sea', in contrast to Irish "muir", Welsh "môr" (Proto-Celtic *mori) < PIE "*móri"; "lacus" 'lake', in contrast to Irish "loch" < PIE "*lókus". De Vaan (2008: 8) suggests a general shift "*o" > "a" in open syllables when preceded by any of "*b", "*m"; "*kʷ", "*w"; "*l". Vine (2011) disputes the cases with "*moCV", but proposes inversely that "*mo-" > "ma-" when followed by "r" plus a velar ("k" or "g").