In this paper, we investigate the average behavior of coefficients of the triple product $L$-function $L(f \otimes f \otimes f,s)$ attached to a primitive holomorphic cusp form $f(z)$ of weight~$k$ for the full modular group $SL(2, \Z )$. Here we call $f(z)$ a primitive cusp form if it is an eigenfunction of all Hecke operators simultaneously.
Guangshi Lü. Ayyadurai Sankaranarayanan. "On the coefficients of triple product $L$-functions." Rocky Mountain J. Math. 47 (2) 553 - 570, 2017. https://doi.org/10.1216/RMJ-2017-47-2-553