Origami Design Secrets : Mathematical Methods for an Ancient Art, Second EditionLang · Revised.2011PDF11 MB
The Night Sky Companion - a Yearly Guide to Sky-watchning 2008-2009Lang · Patrick Moore's practical astronomy series2007PDF49 MB
Origami 5 : Fifth International Meeting of Origami Science, Mathematics, and EducationWang-Iverson et al. · CRC Press (Unlimited)2011PDF36 MB
Growing Together: Personal Relationships Across the Life Span (advances in Personal Relationships)Lang et al. · November 102003PDF7.6 MB