If the publication date of a resource is not identifiable cite the date as n.d.
MathTeaching.org n.d., Math teacher resources: lesson plans, games & more, MathTeaching.org, viewed 17 March 2018, <https://www.mathteaching.org/math-teacher-resources-lesson-plans-games-more/>.
Richmond Landcare n.d., Fact sheet: green tree frogs, New South Wales Government, viewed 17 March 2018, <https://www.rous.nsw.gov.au/page.asp?f=RES-FOW-50-44-25>.
Richmond Landcare (n.d.) have noted ...
Note: The letters a, b, etc are given in order of the appearance in the reference list, regardless of what order they appear in the text.
Allan, MS 1983a, 'Uses of video recording in an institution', in J McGovern (ed.), Video applications in English language teaching, Pergamon, London, pp. 83-93.
Allan, MS 1983b, 'Viewing comprehension with video', ELT Journal, vol. 37, no.1, pp. 23-7.
Collins, M 2000, Really interesting stuff, Penguin, London.
Collins, M 2005, More really interesting stuff, Penguin, London.
Collins, M & Adams, A 1995, Not so interesting stuff, Penguin, London.
Collins, M & Smith, A 1990, Stuff that's kind of interesting in parts, Penguin, London.
This is known as 'secondary referencing'.
It would be preferable to find the original quote to examine the context in which it was written. If that isn't possible use this format.
In this example you have seen Olsen's book. In it she quotes something by Wembley.
Author of the quote (Year, cited in Author of resource you have seen, year, page no.)
Include the author and year of both texts, and the page of the citation you are quoting from.
Wembley (1997, cited in Olsen 1999, p. 156) argues that impending fuel shortages ...
Only include a reference for the resource that you have actually seen, in this case Olsen.
Olsen, M 1999, My career, Gallimard, Paris.
We acknowledge the Australian Aboriginal and Torres Strait Islander peoples as the first inhabitants of the nation and acknowledge Traditional Owners of the lands where our staff and students, live, learn and work.