John writes:

>On Sun, 7 May 2000 xpolakis@... wrote:

>>

>> >This is an old problem, first solved by a Duchman math/an (name?),

>> >and by Conway (and Somebody ?).

>

> No, I didn't solve this problem, although I did do some work

.... which work, according to experts on this problem, was crucial, since...

(see below)

>on it. It was completely solved about 5 years ago by Bjorn(?) Poonen

>and Mike Rubinstein.

>

> John Conway.

Today I quoted Heineken:

| This problem was given by the Dutch Mathematical Society in the 30's,

| and one solution was given by G. Bol. Unfortunately, his solution published

| in _Archief voor Wiskunde_, escaped the attention of many mathematicians,

| so many articles on this problem or its specific cases appeared;

| for example, by Conway and Goft, Heineken, and Harborth.

^^^^

It is a misspelling but not of mine. The name I think is Croft.

Antreas