Haeckel, Ernst (1866). Generelle Morphologie der Organismen [The General Morphology of Organisms](en alemán). vol. 2. Berlin, (Germany): Georg Reimer. From p. 286: "Unter Oecologie verstehen wir die gesammte Wissenschaft von den Beziehungen des Organismus zur umgebenden Aussenwelt, wohin wir im weiteren Sinne alle "Existenz-Bedingungen" rechnen können." (By "ecology" we understand the comprehensive science of the relationships of the organism to its surrounding environment, where we can include, in the broader sense, all "conditions of existence".)
Cooper, W. S. (1957). «Sir Arthur Tansley and the Science of Ecology». Ecology38 (4): 658-659. doi:10.2307/1943136.
Smith, Christopher C. (September 1988). «Elements of Ecology Robert Leo Smith». The American Biology Teacher50 (6): 394. ISSN0002-7685. doi:10.2307/4448774.
Lloyd, David G.; Schoen, Daniel J. (1992). «Self- and Cross-Fertilization in Plants. I. Functional Dimensions». International Journal of Plant Sciences153 (3, Part 1): 358-369. doi:10.1086/297040.
doi.org
Nieder, J., Prosperí, J. & Michaloud, G. Epiphytes and their contribution to canopy diversity. Plant Ecology 153, 51–63 (2001). https://doi.org/10.1023/A:1017517119305
Smith, Christopher C. (September 1988). «Elements of Ecology Robert Leo Smith». The American Biology Teacher50 (6): 394. ISSN0002-7685. doi:10.2307/4448774.