The authors introduce the notions of Ritt order and lower order to functions defined by the series (The equation is abbreviated) exp(-λ_ns) where (λ_n) is a D-sequence and f_n(s) are entire functions of bounded index.
孫以臻(2017)。In the Name of Curating〔碩士論文,國立臺北藝術大學〕。華藝線上圖書館。https://www.airitilibrary.com/Article/Detail?DocID=U0014-0602201700004700
YANG, D., & LIU, J. (1999). ON A CLASS OF UNIVALENT FUNCTIONS. International Journal of Mathematics and Mathematical Sciences, 1999(), 605-610. https://doi.org/10.1155/S0161171299226051
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