Ika Darnhofer, editor
Farming systems research into the 21st century : the new dynamic
[, Springer], 2012
 eBooks
Nugent William R.
Practice Evaluation for the 21st Century
Thomson Learning, 2001
 Buku Teks
Lawal, Ibironke O.
Library and information science research in the 21st century : a guide for practising librarian and students
Chandos Publishing, 2009
 Buku Teks
Niles, Spencer G.
Career development interventions in the 21st century
Pearson, 2013
 Buku Teks
Chorafas, Dimitris N.
Operation research for industrial management
Reinhold Publishing Corporation, 1958
 Buku Teks