[MSDN Library June 1998] WM_USER (40.0499537999538%)

MSDN Library Visual Studio 6.0 > Platform SDK > User Interface Services > Windowing > Messages and Message Queues > Messages and Message Queues Reference > Messages and Message Queues Messages

[MSDN Library April 2000] WM_USER (40.0499537999538%)

MSDN Library - April 2000 > Platform SDK > User Interface Services > Windows User Interface > Windowing > Messages and Message Queues > Messages and Message Queues Reference > Messages and Message Queues Messages

[MSDN Library April 2000] WM_USER (39.0136179609864%)

MSDN Library - April 2000 > Windows CE Documentation > Application Development > API Reference > User Interface > Messages