| http://electric-watches.co.uk/ | Great web site dedicated to Electric watches |
https://www.explainthatstuff.com/quartzclockwatch.html
| How quartz clocks work |
| http://www.elitetimepieces.com/research.html | Serial number/year on many brands |
| https://watchspace.co.uk/about/ | A fellow watch fans web pages – great ! – see e.g links to serial nr/years |
| https://omegaforums.net/ | Omega Forum |
| https://www.theseikoguy.com/ | The Seiko guy – great site |
| https://www.plus9time.com/ | Seiko and other Japanese watches |
| https://www.watchhunter.org/ | Seiko catalogues from 66’ up to today! |
| https://www.timeline.watch/ | Dan Henry, collector, great watch timeline |