Haiman J. Concessives, conditionals, and verbs of volition // Foundations of Language: International Journal of Language and Philosophy. Vol. 11. No3. 1974. P. 341-359.
König E. Conditionals, concessive conditionals and concessives: areas of contrast, overlap and neutralization // On conditionals / Ed. E.C. Traugott [et al.]. Cambridge, 1986. P. 222-246.
König E. Concessive Clauses // Encyclopedia of Language and Linguistics. 2-nd edition / Ed. K. Brown [et al.]. Vol. 2. Amsterdam; Boston; Heidelberg etc., 2006. P. 820-824.