footnote

README.md

@@ -20,6 +20,17 @@ a sorted list of all `f x y`, for each `x` in `xs` and `y` in `ys`.
 
 With `applyMerge`, we can implement a variety of complex algorithms succinctly.
 For example, the Sieve of Erastosthenes[^1] to generate prime numbers:
+
+[^1]: Note that this is really the Sieve of Erastosthenes, as defined in the
+classic [The Genuine Sieve of Eratosthenes](https://www.cs.hmc.edu/~oneill/papers/Sieve-JFP.pdf).
+Constrast this to other simple prime generation implementations, such as
+```
+primes = sieve [2..]
+sieve (p : xs) = p : sieve [x | x <− xs, x ‘mod‘ p > 0]
+```
+which is actually trial division, and not a faithful implementation of the Sieve
+of Erastosthenes.
+
 ```haskell
 primes :: [Int]
 primes = 2 : ([3..] `minus` composites)    -- `minus` from data-ordlist
@@ -44,7 +55,6 @@ overwritten.
 
 See [ALGORITHM.md](docs/ALGORITHM.md) for a full description of the algorithm.
 
-[^1]: (Note that this is really the Sieve of Erastosthenes, as defined in the classic  [The Genuine Sieve of Eratosthenes](https://www.cs.hmc.edu/~oneill/papers/Sieve-JFP.pdf), and not trial division).
 
 ## Licensing
 This project licensed under BSD-3-Clause (except for `.gitignore`, which is