Cassel, Paul
Teach yourself Windows 98 in 21 days
SAMS Pub., 1998
Buku Teks
Arnush, Craig
Teach yourself Turbo C++ 4.5 for Windows in 21 days
Sams Pub., 1995
Buku Teks
Mahar, Paul
Teach yourself IntraBuilder in 21 days / Paul Mahar, Ken Henderson
Sam.net Publishing, 1997
Buku Referensi
Nanang Qosim Yusuf
21 Days to be trans human: panduan menjadi manusia di atas rata-rata
Zaman, 2011
Buku Teks
Schlesinger, Arthur Meier
A Thousand days
A Marner Book, 2003
Buku Teks