Table B.1: Atomic data references for CEL analysis.

Ion	Transition probabilities	Collision strengths
C  II	Nussbaumer & Storey (1981a)	Blum & Pradhan (1992)
C  III	Keenan et al. (1992)	Keenan et al. (1992)
	Fleming et al. (1996)
C  IV	Wiese et al. (1966)	Gau & Henry (1977)
N  II	Nussbaumer & Rusca (1979)	Stafford et al. (1994b)
N  III	Fang et al. (1993)	Blum & Pradhan (1992)
		Stafford et al. (1994a)
N  IV	Nussbaumer & Rusca (1979)	Mendoza (1983)
N  V	Wiese et al. (1966)	Osterbrock & Wallace (1977)
O  II	Zeippen (1982)	Pradhan (1976)
O  III	Nussbaumer & Storey (1981b)	Aggarwal (1983)
O  IV	Nussbaumer & Storey (1982b)	Zhang et al. (1994)
		Hayes & Nussbaumer (1984)
Ne  II	Mendoza (1983)	Bayes et al. (1985)
Ne  III	Mendoza (1983)	Butler & Zeippen (1994)
Ne  IV	Zeippen (1982)	Giles (1981)
Ne  V	Froese & Saha (1985)	Lennon & Burke (1994)
S  II	Mendoza & Zeippen (1982b)	Keenan et al. (1996)
	Keenan et al. (1993)
S  III	Mendoza & Zeippen (1982a)	Mendoza (1983)
S  IV	Storey (unpublished)	Butler & Zeippen (1989)
Cl  III	Mendoza (1983)	Mendoza (1983)
Cl  IV	Mendoza & Zeippen (1982b)	Butler & Zeippen (1989)
Cl  V	Mendoza (1983)	Mendoza (1983)
Ar  II	Pelan & Berrington (1995)	Vujnovic & Wiese (1992)
Ar  III	Mendoza & Zeippen (1983)	Johnson & Kingston (1990)
Ar  IV	Mendoza & Zeippen (1982b)	Zeippen et al. (1987)
Ar  V	Mendoza & Zeippen (1982a)	Mendoza (1983)
Ar  VI	Storey (unpublished)	Saraph & Storey (1996)
Mg  IV	Mendoza & Zeippen (1983)	Saraph & Tully (1994)
Mg  V	Galavis et al. (1997)	Butler & Zeippen (1994)
Fe  III	Nahar & Pradhan (1996)	Zhang (1996)
Fe  IV	Garstang (1958)	Zhang & Pradhan (1997)
	Fischer & Rubin (2004)
Fe  VI	Nussbaumer & Storey (1978)	Nussbaumer & Storey (1978)
Fe  VII	Nussbaumer & Storey (1982a)	Keenan & Norrington (1987)
		Berrington et al. (2000)