Start at the top, and move diagonally down and to the right. Letters advance through the alphabet in steps of 5 then 6. Continue this pattern, starting with the next circle down on the left etc.

Start on the bottom left and move up to the top, then to the right one space and down to the bottom. Letters follow the alphabetic sequence alternately in steps of 6, then 8. Starting on the bottom right and moving up to the top, then left one space and down to the bottom, letters in this half follow the same pattern.

Split the diagram in half horizontally and vertically. Start in the top left square of each quarter, and move clockwise around the other squares in the quarter. In each quarter, letters advance through the alphabet in steps of 2 for the upper left quarter, 3 for the upper right, 4 for the lower right and 5 for the lower left.

Starting at the left and working to the right, letters move through the alphabet in steps of 8 letters, then 9, then 10 etc.

Start with the D on the outer left of the diagram, and move clockwise around the outer segments, then start on the N anti-clockwise around the inner segments. Letters advance through the alphabet in steps of 3, then 4, 5, and 6, repeating this sequence.

In each circle, the reverse alphabetical value of the lower letter equals the sum of the alphabetical values of the top 2 letters.