Dragomir, S. S. “Representation of Continuous Linear Functionals on Smooth Reflexive Banach Spaces”. Anal. Numér. Théor. Approx., vol. 16, no. 1, Feb. 1987, pp. 19-28, https://ictp.acad.ro/jnaat/journal/article/view/1987-vol16-no1-art3.