APA Style
Kretzmann, P, E, (, E. ([19--]).
John Ludwig Krapf : the explorer-missionary of northeastern Africa .
Columbus, O.:
The Book Concern.
MLA Style
Kretzmann, Paul, E., (Paul, Edward).
"John Ludwig Krapf : the explorer-missionary of northeastern Africa".
Columbus, O.:
The Book Concern,
[19--].
Text.