Article: implicit possessor

ὥσπερ γὰρ οἱ ποιηταὶ τὰ αὑτῶν ποιήματα καὶ οἱ πατέρες τοὺς παῖδας ἀγαπῶσιν, ταύτῃ τε δὴ καὶ οἱ χρηματισάμενοι περὶ τὰ χρήματα σπουδάζουσιν ὡς ἔργον ἑαυτῶν

For just as poets love their own poems and fathers love their children, so also people who have earned money take this money seriously as their own work.

If the possessor is apparent from the context or from nature, Greek usually uses an article instead of a possessive pronoun.

Historical background

Over the course of time the proportion of possessive pronouns steadily increases. In the New Testament, for example, possessive pronouns are much more common than articles.

Example Sentences: 

καὶ ὁ μὲν γηραιὸς τελευτήσας ἐν Ἐφρὰν τῇ πατρίδι θάπτεται

And after the old man had died, he was buried in the town of his father, Ophra.