Five Simple Steps to Designing Grid Systems: Subdividing Ratios
http://www.markboulton.co.uk/journal/comments/five_simple_steps_to_designing_grid_systems_part_1/

Boulton, Mark
Mark Boulton
2007

Abstract:

Ratios are at the core of any well-designed grid system. Sometimes those ratios are rational, such as 1:2 or 2:3, others are irrational such as the 1:1.414 (the proportion of A4). This first part is about how to combine those ratios to create simple, balanced grids which in turn will help you create harmonious compositions.