need some paper

1. "digital modulation using the NCMO",robert j zavrel, rf design , march 1988

2. "frequency modulation design for direct digital synthesizers",earl w macune rf expo east proceedings 1989

3. "audio to rf : a completely digital fm broadcast stereo system",robert j zaverel jr 43rd annual broadcast engineering conference proceedings national association of broadcasters 1989.
thakns in advance