Here is the verse that states that all Muslim women should wear the "hijab":

And say to the believing women that they should lower their gaze and guard their modesty; that they should not display their beauty and ornaments except what (must ordinarily) appear thereof; that they should draw their veils over their bosoms and not display their beauty except to their husbands, their fathers, their husband´s fathers, their sons, their husbands´ sons, their brothers or their brothers´ sons, or their sisters´ sons, or their women, or the slaves whom their right hands possess, or male servants free of physical needs, or small children who have no sense of the shame of sex; and that they should not strike their feet in order to draw attention to their hidden ornaments. And O ye Believers! turn ye all together towards Allah, that ye may attain Bliss. [Sura: 24, Verse: 31]

I just want to clarify something to the people who wonder why Muslims do things like the women wearing hijab. Of course, wearing hijab is not the best appearance of women but according to Muslims, life is a test which is full of temptations and desires that you have to leave some of them (Haram things) for the sake of Allah so that Allah rewards you the Paradise in the next life, so you don´t always have the do the things you want or things that please you whatever the consequences.

And this meaning is stated in Quran in various verses:

What is the life of this world but play and amusement? But best is the home in the hereafter, for those who are righteous. Will ye not then understand? [Sura: 6, Verse: 32].

The (material) things which ye are given are but the conveniences of this life and the glitter thereof; but that which is with Allah is better and more enduring: will ye not then be wise? [Sura: 28, Verse: 60]

O men! Certainly the promise of Allah is true. Let not then this present life deceive you, nor let the Chief Deceiver deceive you about Allah. [Sura: 35, Verse 5]

"O my people! This life of the present is nothing but [temporary] convenience: It is the Hereafter that is the Home that will last. [Sura: 40, Verse: 39]

Know ye [all], that the life of this world is but play and amusement, pomp and mutual boasting and multiplying, [in rivalry] among yourselves, riches and sons. Here is a similitude: How rain and the growth which it brings forth, delight [the hearts of] the tillers; soon it withers; thou wilt see it grow yellow; then it becomes dry and crumbles away. But in the Hereafter is a Penalty severe [for the devotees of wrong]. And Forgiveness from Allah and (His) Good Pleasure (for the devotees of Allah). And what is the life of this world, but goods and chattels of deception? [Sura: 57, Verse: 20].

The likeness of the life of the present is as the rain which We send down from the skies: by its mingling arises the produce of the earth- which provides food for men and animals: (It grows) till the earth is clad with its golden ornaments and is decked out (in beauty): the people to whom it belongs think they have all powers of disposal over it: There reaches it Our command by night or by day, and We make it like a harvest clean-mown, as if it had not flourished only the day before! thus do We explain the Signs in detail for those who reflect. [Sura: 10, Verse: 24]

Set forth to them the similitude of the life of this world: It is like the rain which we send down from the skies: the earth´s vegetation absorbs it, but soon it becomes dry stubble, which the winds do scatter: it is (only) Allah who prevails over all things. [Sura: 18, Verse 45]

I notice that some people here reveal apparent hostility against Islam and Islamic thoughts showing it like a ghost threatening people´s lives. But this is not true, Islam is not dangerous, it is not harmful. Why are you afraid of Islamic thoughts being spread in Turkey or wherever? Islam doesn´t force anybody to believe or to do what they don´t want to do. I´ve read the article sent by Roswitha www.meforum.org/article/404 that talks about Gülen and his life and I found that he is not racial, or bigot, or dangerous. Instead, he is moderate and every Muslim has the right to support him or not.

How can i say:
1) Your dog´s collar (The collar of your dog).
2) His/her dog´s collar.
3) their books.

Thank you very much, it is very clear now