%0 Journal Article
%T Characteristic function of a meromorphic function and its derivatives
%J Bulletin of the Iranian Mathematical Society
%I Iranian Mathematical Society (IMS)
%Z 1017-060X
%A Wu, J.
%A Wu, Z.
%D 2013
%\ 12/15/2013
%V 39
%N 6
%P 1117-1123
%! Characteristic function of a meromorphic function and its derivatives
%K characteristic function
%K Nevanlinna's deficiency
%K maximum deficiency sum
%R
%X In this paper, some results of Singh, Gopalakrishna and Kulkarni (1970s) have been extended to higher order derivatives. It has been shown that, if $sumlimits_{a}Theta(a, f)=2$ holds for a meromorphic function $f(z)$ of finite order, then for any positive integer $k,$ $T(r, f)sim T(r, f^{(k)}), rrightarrowinfty$ if $Theta(infty, f)=1$ and $T(r, f)sim (k+1)T(r, f^{(k)}), rrightarrowinfty$ if $Theta(infty, f)=0.$
%U http://bims.iranjournals.ir/article_464_28b526931ff60ee50847aaedcce35cc0.pdf