Rule: Possessive adjectives only co-occur with restrictive relative clauses if the meaning of the clause is clearly partitive.
Examples of errors:
(1) A lot of his papers he wrote went into the waste basket.
(2) It is not unusual that old ladies put all their money they have saved in pillows.
(3) Thank you for your letter I received today.
(4) We have to develop a critical attitude toward our role we will play as teachers.
Sentences like (l)-(4) should be compared with sentences like:
I gave all my pencils that had my name on them to Bill
Here the pencils referred to are clearly only a portion of the total number of "my pencils". In contrast, the relative clause he wrote in (1) is not partitive (i.e.. does tot refer to a part or portion of a whole), since he wrote all his papers and not just a portion of them, although grammatically the clause is restrictive i.e. it is not separated from the main clause by pauses, and the relative pronoun is deleted). (2) is somewhat more problematic, because logically the relative clause here may be construed as partitive--they have saved only ,part of their money. It seems that the partitive idea must be clearly emphasized, however, even essential to the meaning of the sentence, in order to allow the possessive premodifier. If we say, for example,
The ladies put all their money that they had earmarked for their retirement in pillows
the partitive sense of the relative clause is clearer, and the possessive their no longer seems odd. There is no way the relative clause in (3) and (4) can be interpreted as partitive, of course, since letter and role are singular count nouns.