The main vocals of A1 are sampled from "Ich sing wie Marusha" (transl. "I'm singin' like Marusha") by Hannelore Cool. Further samples of that track include a sound effect from "I Am The Master (Soul Version)" by Underground Nation Of Rotterdam and a melody line from "Knor" by Sigma 909.
B1 samples Run-DMC – King Of Rock
This release was reissued about two weeks later with a slightly differently produced version of A1. Most significantly the main vocals were replaced and one other sample was removed. Apparently the track was modified due to copyright issues about these samples.