With relative pronouns prepositions can be used. In English there are two possibilities - with whom the preposition is put before the relative pronoun; with that the preposition is put behind the verb. With who and which it can have both positions:

The man to whom we were talking in the train was an architect.
The man who we were talking to in the train was an architect.
The man that we were talking to in the train was an architect.
The book to which I was referring is quite expensive.
The book, which I was referring to is quite expensive.
The book that I was referring to is quite expensive.

In Spanish, the system is a bit simpler. The preposition is put before the relative pronoun. Next in line is the article (in right gender and number according to the referred object!) and then the verb.

In Spanish things are different. Prepositions do not require a special declension. The are adapted to
number and gender of the object, which is referred to. The complete overview looks as follows.

	preposition	+ article            +  relative pronoun           +			verb
		que	cual	quien
el hombre los hombres la mujer las mujeres	por de enfrente delante encima sobre con            etc.	(d)el que (de) los que (de) la que (de) las que	(d)el cual (de) los cuales (de) la cual (de) las cuales	(de) quien	hablamos                          etc.

La mujer para la que yo diseño no es una compradora compulsiva, ni una fashion victim que pasa horas arreglándose. = The woman that I design for is neither a compulsive buyer nor a fashion victim that spends hours dressing up. Descubre la nueva fragancia especialmente creada para la mujer para la que todo momento cuenta. = He discovered the new fragrance especially created for a woman for who every moment counts.