From a Frank Horwill article:
Dr Van Aaken is noted for his LSD (Long Slow Distance) theory. Many thought his views were outlandish, but he coached two world-record holders with his methods. His view was that distance runners should aim to be 20 per cent below average weight for their height, and to achieve this they should limit their fat intake to 35 grams a day and run a certain mileage daily commensurate with their event in order to burn off calories. He drew up a mileage table as follows:
400m runner, 4 miles; 800m runner, 6 miles; 1,500m runner, 10 miles; 5km runner, 15 miles; 10km runner, 18 miles; marathoner, 26 miles.
Now this may look like a recipe for one-pace running. But he added a significant corollary: three times a week after these outings, run a section of your event at race pace, eg, 1 x 350m for the 400m athlete, 1 x 400m for the 800m runner, 1 x 800m for the 1,500m runner, 1 x mile for the 5km specialist, 1 x 2 miles for the 10km runner and 1 x 10km for the marathoner.
http://www.serpentine.org.uk/advice/coach/fh02.php
The book that was published in the US back in the 70s (The Van Aaken Method) is readily available at used books sites online.
For a modern interpretation on the Van Aaken method check out the books/work of Phil Maffetone -- who worked with Mark Allen among others.
http://www.rrca.org/publicat/slowdown.html