In the context of relativistic quantum mechanics, where the Schr\"odinger
equation is replaced by the spinless Salpeter equation, we show how to
construct a large class of upper limits on the critical value,
gc(ℓ), of the coupling constant, g, of the central potential,
V(r)=−gv(r). This critical value is the value of g for which a first
ℓ-wave bound state appears.Comment: 8 page