Genesis 6 1-4 Jerusalem Bible

the King James version:

There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men which were of old, men of renown.
Genesis 6, Verse 4

the Jerusalem Bible version:

Sons of God and daughters of men
When men had begun to be plentiful on the earth, and daughters had been born to them, the sons of God, looking at the daughters of men, saw they were pleasing, so they married as many as they chose. Yahweh said, 'My spirit must not for ever be disgraced in man, for he is but flesh; his life shall last no more than a hundred and twenty years'. The Nephilim were on the earth at that time (and even afterwards) when the sons of God resorted to the daughters of man, and had children by them. These are the heroes of days gone by, the famous men.
Genesis 6: 1-4

The Jerusalem Bible passage is just as mysterious as the King James, but I'm not straining to decipher the pronoun referents.