EPG describes items constructed from a reference system consisting of n points and/or n lines, where n ≥ 3.

When n = 3, this corresponds to the triangular case, where the reference system is based on either three points or three lines. This case has been extensively documented in the literature.

Three primary sources are:
ETC — Encyclopedia of Triangle Centers  by Clark Kimberling
CTC — Catalogue of Triangle Cubics  by Bernard Gibert
MathWorld — Mathematical reference work  by Eric W. Weisstein

Within EPG, triangle-related information will primarily be referenced through these established sources. The following table summarizes the generic EPG-style codings for triangle-based elements:

 

Generic Code	Description	Source	Presentation	Example Code	Example Name	Reference
TR-Px	Triangle Points	ETC	X(nnn)	X(1)	Incenter	Ref‑1a
		MathWorld	Alphabetic list	—	Orthocenter	Ref‑1b
TR-2Px	Triangle Bicentric Pairs	ETC	P(nnn)	P(1)	Brocard Points	Ref‑2
TR-Lx	Triangle Lines	ETC	Numerical list	Line(44)	Eulerline	Ref‑3a
		MathWorld	Alphabetic list	—	Brocard Axis	Ref‑3b
TR-Trx	Triangle Triangles	ETC	Alphabetic list	—	Intouch Triangle	Ref‑4a
		MathWorld	Alphabetic list	—	Medial Triangle	Ref‑4b
TR-Tfx	Triangle Transformations	ETC	Alphabetic list	—	Isogonal Conjugate	Ref‑5
TR-Cix	Triangle Circles	MathWorld	Alphabetic list	—	Circumcircle	Ref‑6
TR-Cox	Triangle Conics	MathWorld	Alphabetic list	—	Steiner Inellipse	Ref‑7
TR-Cux	Triangle Cubics	CTC	Knnn	K001	Neuberg Cubic	Ref‑8a
		MathWorld	Alphabetic list	—	Darboux Cubic	Ref‑8b
TR-Cvx	Triangle Higher Degree Curves	CTC	Qnnn	Q000	Steiner Deltoids	Ref‑9
TR-Pfx	Triangle Perspective Fields	EPG	PF[Xi,Xj,Xk;Xl]	PF[X13,X2,X6;X15]	Main Perspective Field	TR-Pf0
TR-Plsx	Triangle Persp. Linear Sets	EPG	PLS[Xi,Xj;Xk]	PLS[X2,X4;X3]	Main Eulerline Linear Set	TR-Pf0