<P> IF y = Citations y − 1 + Citations y − 2 Publications y − 1 + Publications y − 2 (\ displaystyle (\ text (IF)) _ (y) = ((\ text (Citations)) _ (y - 1) + (\ text (Citations)) _ (y - 2) \ over (\ text (Publications)) _ (y - 1) + (\ text (Publications)) _ (y - 2))) </P> <P> For example, Nature had an impact score of 41.456 in 2014: </P> <P> IF 2014 = Citations 2013 + Citations 2012 Publications 2013 + Publications 2012 = 29753 + 41924 860 + 869 = 41.456 (\ displaystyle (\ text (IF)) _ (2014) = ((\ text (Citations)) _ (2013) + (\ text (Citations)) _ (2012) \ over (\ text (Publications)) _ (2013) + (\ text (Publications)) _ (2012)) = (29753 + 41924 \ over 860 + 869) = 41.456) </P> <P> This means that, on average, its papers published in 2012 and 2013 received roughly 41 citations each in 2014 . Note that 2014 impact factors are reported in 2015; they cannot be calculated until all of the 2014 publications have been processed by the indexing agency . </P>

What do you mean by citation and impact factor