(left) A multi-valued (upper branch of) the dispersion curve leads to bistability of waves for T = 30, β = 8, κ = 0.96, τ = 7, θ = 0.3. The blue profile has c=1.215 and the red profile has c=0.812. Note that the profile of the slower wave has an additional oscillation near the steady state. (right) Creation of isolas and dispersion gaps. There are no T-periodic waves for 30.34<T<31.7 with β=8,κ=1.15, τ=10,θ=0.3.