Abbreviations you can use when you can't locate all the referencing details:
No author is given use [Anon.]
No date of publication is given use [n.d.]
No place of publication is given use [s.l.]
No publisher is given use [s.n.]
Something other is not known use [n.k.]
Turnitin is plagiarism detection software. It matches documents against a large database of websites, published information and other people's work.
Only use et al. in the main part of your assignment when there are 3 or more authors.