Further Formulas for Calculating Approximate Values of the Zeros of Certain Combinations of Bessel Functions (Correspondence)

In a recent letter Gunston has presented a wonderfully simple approximate formula for the smallest z zero of the Bessel function equation J_p(z) N_p (kz) - J_p(kz)N_p(z) =0(1) where J_p and N_p are, respectively, the Bessel functions of the first and second kinds of real-order p. This communication is intended to draw attention to the existence of similar approximate formulas for both the larger z zeros of (1) and the roots of the equally-important companion equationJ´/spl_p(z) N´_p (kz) - J´_p(kz)N´_p(z) =0 (2) where ´ indicates differentiation.