https://arxiv.org/abs/1512.04165
[1512.04165] Comparable upper and lower bounds for boundary values of Neumann eigenfunctions and...
Abstract page for arXiv paper 1512.04165: Comparable upper and lower bounds for boundary values of Neumann eigenfunctions and tight inclusion of eigenvalues
upper and lower bounds
https://www.unsw.edu.au/science/our-schools/maths/engage-with-us/seminars/2024/On-explicit-upper-and-lower-bounds-for-the-Selberg-class-functions
On explicit upper and lower bounds for the Selberg class functions
upper and lower boundsfor theselberg classexplicit