1. W. E. Milne, A theorem of oscillation,Bull. Amer. Math. Soc.,28 (1922), pp. 102–104.
2. In order to prove the oscillating character of the solution, it is sufficient to assume instead of “f(y) is odd” that sgf(y)=sgy.
3. E. G.h(u) may be an even function decreasing foru≥0.
4. Similarly, it may readily be seen thatall the solutions of (1) have this character, provided thatb is large enough compared to η.
5. Iff(y) is like that in footnote2, then the maxima form a decreasing sequence and similarly the minima form another one.