PMEG is a book with the title [_Plena manlibro de Esperanta gramatiko_](https://bertilow.com/pmeg/index.html). The current main editor is [Bertil Wennergren](https://eo.wikipedia.org/wiki/Bertilo_Wennergren), a known Esperantist and music performer. PMEG or PoMeGo, the big apple, is available online and is considered by many the most comprehensive grammar book.