  We document the creation of a data set of 16,627 archived web pages, or
mementos, of 3,698 unique live web URIs (Uniform Resource Identifiers) from 17
public web archives. We used four different methods to collect the dataset.
First, we used the Los Alamos National Laboratory (LANL) Memento Aggregator to
collect mementos of an initial set of URIs obtained from four sources: (a) the
Moz Top 500, (b) the dataset used in our previous study, (c) the HTTP Archive,
and (d) the Web Archives for Historical Research group. Second, we extracted
URIs from the HTML of already collected mementos. These URIs were then used to
look up mementos in LANL's aggregator. Third, we downloaded web archives'
published lists of URIs of both original pages and their associated mementos.
Fourth, we collected more mementos from archives that support the Memento
protocol by requesting TimeMaps directly from archives, not through the Memento
aggregator. Finally, we downsampled the collected mementos to 16,627 due to our
constraints of a maximum of 1,600 mementos per archive and being able to
download all mementos from each archive in less than 40 hours.
