MP4L might be an acronym. Let me think. In Belgium, there's the Ministry of Justice, but I'm not sure about the exact department in 1991. Alternatively, MP4L could stand for something like "Migration Policy Framework," but that's a stretch. Maybe there's a specific task force or working group named MP4L related to the Voorlichting in 1991? Without direct knowledge, this could be challenging. I might need to look up historical references or news articles from that time.