Heidegger's 'On the Essence and Concept of Physis in Aristotle's Physics B, I': (1) Opening section: initial discussion of concepts of “nature” and physis.

http://religiousstudies.stanford.edu/WWW/Sheehan/pdf/heidegger_texts_online/1929%20WHAT%20IS%20METAPHYSICS.pdf
http://religiousstudies.stanford.edu/WWW/Sheehan/pdf/heidegger_texts_online/1940%20PHYSIS.pdf
http://religiousstudies.stanford.edu/WWW/Sheehan/pdf/heidegger_text

http://www.lancaster.ac.uk/users/philosophy/awaymave/408new/wk9.htm
http://ebooks.cambridge.org/chapter.jsf?bid=CBO9780511812637&cid=CBO9780511812637A025
http://ebooks.cambridge.org/chapter.jsf?bid=CBO9780511812637&cid=CBO9780511812637A016