@unpublished{lamport2000lower,
author = {Lamport, Leslie},
title = {Lower Bounds on Consensus},
year = {2000},
month = {March},
abstract = {This short note is described by its abstract: 

We derive lower bounds on the number of messages and the number of message delays required by a nonblocking fault-tolerant consensus algorithm, and we show that variants of the Paxos algorithm achieve those bounds.  
I sent it to Idit Keidar who told me that the bounds I derived were already known, so I forgot about it.  About a year later, she mentioned that she had cited the note in: 

Idit Keidar and Sergio Rajsbaum.  On the Cost of Fault-Tolerant Consensus When There Are No Faults - A Tutorial.  MIT Technical Report MIT-LCS-TR-821, May 24 2001.  Preliminary version in SIGACT News 32(2), Distributed Computing column, pages 45-63, June 2001 (published in May 15th).  
I then asked why they had cited my note if the results were already known.  She replied, 

There are a few results in the literature that are similar, but not identical, because they consider slightly different models or problems.  This is a source of confusion for many people. Sergio and I wrote this tutorial in order to pull the different known results together. Hopefully, it can help clarify things up.},
url = {http://approjects.co.za/?big=en-us/research/publication/lower-bounds-consensus/},
}