found:LCCN 61-19860: His Selected scientific papers, 1960(hdg.: Pol, Balthasar van der, 1889-1959)
found:His Operational calculus, 1987:t.p. (Balth. van der Pol, D. Sc., Dir. of the International Radio Consultative Committee, Geneva; formerly prof. of Theor. Electrotechn. in the Techn. Hogeschool, Delft, Netherlands)
found:Operat︠s︡ionnoe ischislenie na osnove dvustoronnego preobrazovanii︠a︡ Laplasa, 1952:t.p. B. van der Polʹ)