Educational series - Pennsylvania Geologic Survey.

no.5 1961; no.1 1962; no.2 1962; no.3 1962; no.4 1962; no.5 1962; no.6 1962; no.1-7 (1962-68); v.1-8 (1962-1968); no.3 1970; no.8 (1973); no.8-9 1968-1979; no.1, 3rd ed. (rev) 1997; v.9 (1979); v.10 (1989); no.1 1991; v.1 (1991); no.4, 2nd ed. (2nd printing) 1997; no.5 7th printing (rev) 1997; no.10-11 1989-1999; 1-6 1991-99; no.2, 2nd ed. 1999; no.3, 3rd ed. 1999; no.9 2001; no.12 2001; no.4 2002; no.7 2002; no.8 2002; no.10 2003; v.9 (2003); no.1 2004; no.8, 2nd ed, 3rd pr 2007