Smith, Christopher C. (september 1988). "Elements of Ecology Robert Leo Smith". The American Biology Teacher. 50 (6): 394. DOI:10.2307/4448774. ISSN0002-7685. JSTOR4448774.
Smith, Christopher C. (september 1988). "Elements of Ecology Robert Leo Smith". The American Biology Teacher. 50 (6): 394. DOI:10.2307/4448774. ISSN0002-7685. JSTOR4448774.
Smith, Christopher C. (september 1988). "Elements of Ecology Robert Leo Smith". The American Biology Teacher. 50 (6): 394. DOI:10.2307/4448774. ISSN0002-7685. JSTOR4448774.