scientific article published in 1977

scientific article published in 1979

scientific article published in 1975

article by Norman MacLaren Denson et al published 1955 in Coal Investigations

scholarly article published 1965

scientific article published in 1974

article by Norman MacLaren Denson et al published 1955 in Coal Investigations

scholarly article by George O. Bachman published in January 1981

scholarly article by George O. Bachman published in January 1968

article

scholarly article

article