LQR policy gradient:
https://arxiv.org/pdf/1801.05039.pdf

LQR approximate PI:
https://arxiv.org/pdf/1905.12842.pdf

Two-point estimation:
https://arxiv.org/pdf/1812.08305.pdf

Jump system:
https://arxiv.org/pdf/2002.04090.pdf

Robust control:
https://arxiv.org/pdf/1910.09496.pdf