Inverse of This Laplace Function

H(s) = 1/(s^2+9)^2

My attempt to the solution is not that all impressive. I know i have to use convolution to do it, so far i got this

H(s)= (1/(s^2+9).(1/(s^2+9)^2

$$\frac{1}{(s^2+9)^2}=\frac{1}{s^2+3^2}\frac{1}{s^2+3^2}$$