Stanford Encyclopedia of Philosophy's Existentialism Entry
https://plato.stanford.edu/entries/existentialism/
Here you can find a comprehensive explanation of existentialist concepts.
Stanford Encyclopedia of Philosophy's Existentialist Aesthetics
https://plato.stanford.edu/entries/aesthetics-existentialist/
If you'd like to learn more about Sartre's views on art, the Stanford Encyclopedia of Philosophy has an overview of the existentialist philosophy of art.
Simone de Beauvoir
https://plato.stanford.edu/entries/beauvoir/
If you're interested in existentialism, feminism, or simply want to learn more about Sartre's long-term partner, the Stanford Encyclopedia offers a comprehensive look at her philosophy.
