deletions | additions       diff --git a/etymology.tex b/etymology.tex  index ef8711f..b9ba1e8 100644  --- a/etymology.tex  +++ b/etymology.tex 
...
1952, defined it solely as an event, while five define it as both  event and attribute.  An active research community investigating computational models of serendipity can be found in information retrieval \cite{Toms2000} and more specifically, in recommender systems. In the latter domain, Herlocker et al. \cite{Herlocker2004} and especially McNee et al. \cite{McNee2006} promoted serendipity as an important factor for user satisfaction, next to accuracy and diversity. There are several definitions of serendipity in this domain \cite{Lu2012}, which all commonly  require the system to recommend an unexpected and useful \cite{Lu2012}, interesting \cite{Herlocker2004}, attractive or relevant \cite{Ge2010} item. In terms of the prior definitions, the problem can be framed as the user's difficulty in finding items that meet his or her interests or demands  within a large and potentially unobservable search space. This problem can also be passive, and items are suggested to support other stakeholder's goals, e.g. to increase sells. Definitions differ in the requirement for novelty, and some researchers \cite{Adamopoulos2011} develop systems for suggesting items that might already be known, but are still unexpected in the current context. There are numerous examples that exhibit features of  serendipity which develop on a social scale rather than an individual  diff --git a/serendipity.pdf b/serendipity.pdf  new file mode 100644  index 0000000..61390cd  Binary files /dev/null and b/serendipity.pdf differ