Arquitetura. Janelas Medivais Good reference.
Architectural drawings of Doors by Annie Standard
Off the Bookshelf Coloring Book: 45+ Weirdly Wonderful Designs to Color for Fun & Relaxation (Coloring Art): Samarra Khaja: 9781617452789: Amazon.com: Books
The BASICS : Perspective by Shattered-Earth.deviantart.com
Beginners pen & ink techniques ~ nice to have your own version on this techniques cause we all draw differently.
The Inspirational Artistic Design Bundle