paper of timer wheel

[zyctree]

i would like to read the code about the detail implementation of timer, found

///
/// # Implementation
///
/// THe time driver is based on the [paper by Varghese and Lauck][paper].
///

but the link to the paper is missing, searching in history, there is a commit that removed this link,
7b53b7b#diff-e7962099c7699aa4d4efb9ac594f0665L82. is there any reason it was removed? seems like it was removed by accident

Btw, this link missing makes cargo doc --document-private-items fail

[Darksonn]

You can find the paper here. This issue will be fixed by #2572.