I solved some problems concerning orthogonal polynomials from chapter four of the book "Classical and Quantum Orthogonal Polynomials in One Variable" by Mourad E. H. Ismail. I would like to find the original source papers these problems came from. I searched through all of the references in the chapter (and many in the back), and I could not find them. The problems are $P_n(x)=\frac{2}{n!\sqrt{\pi}}\int_{0}^{\infty}\exp(-t^2)t^nH_n(xt)\text{d}t$
$\int_{0}^{t}L_n(x(t-x))\text{d}x=\frac{(-1)^nH_{2n+1}(t/2)}{2^{2n}(3/2)_n}$
$\int_{0}^{t}\frac{H_{2n}\left(\sqrt{x(t-x)}\right)}{\sqrt{x(t-x)}}\text{d}x=(-1)^n\pi2^{2n}(1/2)_nL_n(t^2/4)$
where $P_n(x)$ are the Legendre polynomials, $H_n(x)$ are the Hermite polynomials and $L_n(x)=L_n^{(0)}(x)$ are the Laguerre polynomials.
I really would like the original source these problems came from, but any newer source would work too, as I could look through their references to try and find the original paper. Any tips on how to find these things would also be appreciated, as when I try to search "integral relations" I get more in-depth stuff, like the quantum or multilinear/matrix versions of the polynomials.
Thank you!