Bâ, Sylvia Washington, The Concept of Negritude in the Poetry of Léopold Sédar Senghor, Princeton University Press, 1973.

Bâ discusses Senghor's poetry using the concept of
negritude and the background of African philosophy
as her focus.

Hymans, Jacques Louis, Léopold Sédar Senghor: An Intellectual Biography, Edinburgh University Press, 1971.

Very good historical and biographical study that
discusses Senghor's work and thought within the
broader tendencies of African and negritude philosophy.

Sartre, Jean-Paul, "Orphée Noir," in his Situations III, Gallimard, 1949, pp. 229-86.

This essay was Sartre's controversial introduction to
Senghor's 1948 anthology of negritude poets.

Senghor, Léopold Sédar, Anthologie de la nouvelle poésie nègre et malgache de langue française, Presses universitaires de France, 1948.

Senghor's celebrated and influential anthology of
negritude poets.

———, The Collected Poetry, translated by Melvin Dixon...