Yaw calculation from Accelerator, Mag, Gyro (9 inputs)

Hi guys
I have been able to calculate Pitch and Roll from Accelerator. Now I am looking for calculation Yaw from the 9 inputs:
Accelerator_x, Accelerator_y, Accelerator_z ; Magnetometer_x, Magnetometer_y, Magnetometer_z ; Gyroscope_x, Gyroscope_y, Gyroscope_z

Thanks
PS: I tried using "Magnetometer data, pitch and roll" to calculate Yaw, but the result is bad. I trust Gyroscope data is required to smooth Yaw. I do not know the algorithm which utilizes all the 9 inputs including Gyro. Anyone can shed a light ?

Thanks a lot
Bob