On the covariances of outdegrees in random plane recursive trees
  In 2005 Janson, extending earlier work of Mahmoud, Smythe, and Szyma\'nski, established the joint asymptotic normality of the outdegrees of a random plane recursive tree. In particular, he gave an explicit description of the limiting covariance matrix. Our aim here is to provide substantially simplified expression for the limiting covariance matrix. 
H\"useyin Acan, Pawe{\l} Hitczenko
math.CO