Columbia subject headings:
Gruckow, Paul--Diaries.
Natural history--Northwestern States.
Natural history--Prairie Provinces.
Northwestern States--Description and travel.
Prairie Provinces--Description and travel.
Harvard subject headings:
Gruchow, Paul--Diaries.
Natural history--Northwestern States.
Natural history--Prairie Provinces.
Northwestern States--Description and travel.
Prairie Provinces--Description and travel.
Princeton subject headings:
Gruchow, Paul--Diaries.
Natural history--Northwestern States.
Natural history--Prairie Provinces.
Northwestern States--Description and travel.
Prairie Provinces--Description and travel.