| title | ISBN-13 | year of publication |
|---|---|---|
| Geiriadur Cynradd Gomer | 978-1-85902-758-5 | 2014 |
| Geiriadur Gwybod y Geiriau Gomer | 978-1-84851-769-1 | 2015 |
| Geiriadur Mor, Mwy, Mwyaf Gomer | 978-1-84851-768-4 | 2014 |
| Geiriau Lletchwith, Y - A Check-List of Irregular Word Forms and Spelling: A Check-list of Irregular Words and Spelling | 978-1-85902-404-1 | 2009 |
| Llyfr Berfau, Y: Check-list of Welsh Verbs: Welsh-English | 978-1-85902-138-5 | 2011 |
| Llyfr Enwau, Y - Enwau'r Wlad / Check-List of Welsh Place-Names, | 978-1-84323-735-8 | 2007 |
| Pa Arddodiad: A Check-list of Welsh Prepositions | 978-1-85902-764-6 | 2012 |
| Welsh - English, English - Welsh Dictionary | 978-1-84934-047-2 | 2010 |
| Welsh-English English-Welsh Dictionary | 978-1-85534-795-3 | 1997 |
| Welsh-English/English-Welsh Practical Dictionary | 978-0-7818-0781-4 | 1999 |
| Y Llyfr Ansoddeiriau: A Check-list of Welsh Adjectives | 978-1-84323-239-1 | 2003 |
| Y Treigladur: A Check-List of Welsh Mutations | 978-1-85902-480-5 | 2014 |
D G · D. G Lewis · D. Lewis · G L. · G. Lewis · Geraint Lewis
Geddes & Grosset · Gomer Press · Gwasg Gomer · Hippocrene Books · Waverley Books Ltd