These sheets are entirely optional, and provided purely for your own interest.
You don't have to try Sheet 1 before Sheet 2, although Sheet 2 is more advanced and goes into more details.
Some worked solutions / commentary are available on request for students who have attempted the sheets. It is strongly recommended that you attempt the sheets properly first before asking for the commentary.
Anyone who wishes to read the commentary can email david.hodge at gcu.ac.uk. If you wish to ask any questions about the sheets, then feel free to also email the address above.