Francois do you have this one?

Dual Spark Plugs For Stratified-Charge Rotary Engine
Abraham, John; Bracco, Frediano V.
NASA Center for AeroSpace Information (CASI)
LEW-15923; NASA Tech Briefs, 20, P. 79 , 19960601; Jun 1, 1996
Fuel efficiency of stratified-charge, rotary, internal-combustion engine
increased by improved design featuring dual spark plugs. Second spark
plug ignites fuel on upstream side of main fuel injector; enabling
faster burning and more nearly complete utilization of fuel.
Accession ID: 96B10283
Document ID: 19960024427
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Updated/Added to NTRS: 2005-09-30