@article { author = {Wu, J. and Wu, Z.}, title = {Characteristic function of a meromorphic function and its derivatives}, journal = {Bulletin of the Iranian Mathematical Society}, volume = {39}, number = {6}, pages = {1117-1123}, year = {2013}, publisher = {Iranian Mathematical Society (IMS)}, issn = {1017-060X}, eissn = {1735-8515}, doi = {}, abstract = {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 $Theta(infty, f)=0.$}, keywords = {characteristic function,Nevanlinna's deficiency,maximum deficiency sum}, url = {http://bims.iranjournals.ir/article_464.html}, eprint = {http://bims.iranjournals.ir/article_464_28b526931ff60ee50847aaedcce35cc0.pdf} }