The main problem in fleshing out the proof described above is that it seems at first that to construct a statement "p" that is equivalent to ""p" cannot be proved", "p" would somehow have to contain a reference to "p", which could easily give rise to an infinite regress. Gödel's ingenious technique is to show that statements can be matched with numbers (often called the arithmetization of syntax) in such a way that ""proving a statement"" can be replaced with ""testing whether a number has a given property"". This allows a self-referential formula to be constructed in a way that avoids any infinite regress of definitions. The same technique was later used by Alan Turing in his work on the Entscheidungsproblem.