how a tree works.
disks are sent out to each person in level 1, by whoever is organizing the tree.
each of the people assigned in level 1 then makes copies for those in level 2 and posts the disks to them. this is a branch. level 2 does the same for level 3 and so on.
if someone cannot make copies they are called a leaf, they are sent disks by their supplier, but are not expected to make copies for others. this helps some people start a collection, or they might simply be too busy with work, family, etc. to participate as a branch. shown in darker grey.

it is up to those participating to decide if they want either blank disks sending to them from the level below, or if they want to trade ie. have other shows sent in return for their copying of the tree disks. some may be happy to just send the disks for free. it is up to those in each branch to sort this out for themselves - i don't want to impose any rules.

i have tried to keep this tree to two assignments per individual, and to limit international posting as much as possible.