- CHAMPION / https://www.championautoparts.com/
- BOSCH / https://www.boschautoparts.com/en/
- NGK / https://www.ngksparkplugs.com/
- Autolite / https://www.autolite.com/
- HARLEY DAVIDSON / https://www.harley-davidson.com/
- SPLIT FIRE / https://www.thesplitfire.com/
- ACDelco / https://www.acdelco.com/
- DENSO / https://densoautoparts.com/
- The Green Spark Plug Co / https://www.gsparkplug.com/
- Crossreference / https://jp.sparkplug-crossreference.com/
- NGK company History / https://www.ngk.com.au/ngk/history/
- Formula1 Dictionary / https://www.formula1-dictionary.net/
- BG service / https://www.bgservice.com/54.html
- The Old Motor / https://theoldmotor.com/?p=135208
- HISTORY OF DENSO SPARK PLUG / https://am.denso.com/plug-global/products/history/
- Spark Plug Analysis / https://ngk.com.au/technical_info/analysis/
- Autolite – About Us / https://www.autolite.com/about
- Spark Plug Collectors / https://spcoa.net/
- History Blog / https://www.bosch.com/stories/history-blog/
- Spark Plug Gallery / https://spcoa.net/gallery/
- Spark Plugs from 1917 / https://forums.aaca.org/topic/453737-comprehensive-illustrated-article-on-spark-plugs-from-1917/
- Spark Plug History / https://spcoa.net/spark-plug-history/
- How Albert Champion / https://www.hagerty.com/media/automotive-history/how-albert-championed-two-major-spark-plug-brands/
- Antique Spark Plugs / https://www.gasenginemagazine.com/equipment/collecting-antique-spark-plugs/
- Hemmings – NGK / https://www.hemmings.com/stories/ngk/
- Spark Plug Gap Adjustment / https://www.wwag.com/en/garage-basics-spark-plug-gap-adjustment-and-exchanging-spark-plugs-on-harley-davidson-motorcycles
- Harley Spark Plug / https://bobberbrothers.com/pages/harley-davidson-spark-plug-cross-reference/
スパークプラグの参考サイト一覧
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