19 = (Skaggs et al. 2012)
20 = (Zartman and Doe 1981)
24 = (Stos-Gale et al. 1995)
25 = (Begemann et al. 2001)
26 = (Boni and Koeppel 1985)
27 = (Ludwig et al. 1989)
28 = (Marcoux 1998)
29 = (Pomiès et al. 1998)
30 = (Tornos and Chiaradia 2004)
31 = (Santos Zaldeuegui et al. 2004)
32 = (Le Guen et al. 1991)
33 = (Baron et al. 2006)
34 = (Brevart et al. 1982)
35 = (Arribas and Tosdal 1994)
36 = (Yener and Özbal 1986)
37 = (Stos-Gale et al.1996)
38 = (Stacey and Kramer 1975)
39 = (Wagner et al. 1983-4)
40 = (Sayre et al. 1992)
41 = (Barnes et al. 1974)
42 = (Chalkias et al. 1988)
43 = (Swainbank et al. 1982)
44 = (Velasco et al. 1996)
45 = (Jébrak et al. 1998)
46 = (Yener et al. 1991)
47 = (Sayre et al. 2001)
48 = (Hirao et al. 1995)
49 = (Wagner et al. 1992)
50 = (Seeliger et al. 1985)