Rule: An infinitive clause introduced by a wh- word cannot be attached directly to the antecedent noun.
Examples of errors:
(1) The question how to prevent it is difficult to answer.
(2) It is only a question how to consume the products.
(3) A possible solution of the problem how to integrate,the foreign worker into German society could be the foundation of clubs.
(4) The government should distribute information how to save energy.
(5) In this way one might get further information how to deal with children.
(6) She wanted to buy some stamps, but she couldn't find a place where to buy them.
Wh- words include who, what, where, when, why, and how. Whether is also a wh- word, but it seems to be an exception to Rule 1.10.2,, since it does allow an infinitive to follow:
The question/decision/problem (as to) whether to prevent it or not is crucial.
In general, though, a noun like question or problem followed by an infinitive clause in apposition to it requires the preposition of or as to (cf.(l)-(3)). If the infinitive clause is parenthetical, that is, isolated .from the rest of the clause by pauses and intonation, preposition is necessary:
The question/problem--how to prevent it--is crucial.
Alternatively, the infinitive clause can sometimes be converted to a finite non-restrictive relative clause:
This question, which is how to prevent it, is crucial.
In the case of (6) the infinitive clause can be attached directly to the antecedent noun (without where), or converted to a prepositional phrase or a finite relative clause:
She couldn't find a place to buy stamps/in which to buy stamps/where she could buy stamps/*where to buy stamps.