After retracing the Extreme Ghostbusters' initial encounter with Luko, Egon Spengler located a copy of Principia Mathematica at the New York City Public Library. From it, Egon learned much about Luko and Garibaldi's encounter with it.
- On page six of Ghostbusters Volume 2 Issue #11, Luko's depiction in the Principia Mathematica makes a non-canon cameo above the Spectral Almanac.
- ↑ Egon Spengler (2009). Extreme Ghostbusters- The Infernal Machine (1997) (DVD ts. 14:28-14:30). Sony Pictures Home Entertainment. Egon says: "Principia Mathematica by Antonio Garibaldi."
- ↑ Egon Spengler (2009). Extreme Ghostbusters- The Infernal Machine (1997) (DVD ts. 14:34-14:42, 14:49-15:06). Sony Pictures Home Entertainment. Egon says: "At the end of his life, Garibaldi became obsessed with reproducing the mathematical order of the universe. The music of the spheres...One night, he was visited by an angel who inspired him to build the perfect machine. When the machine came to life and attacked him, he realized he'd been tricked into unleashing the demon, Luko. Garibaldi promptly destroyed his creation hoping to trap the demon forever inside what he had named the Infernal Machine."