Meanings of extant letters in English

Oliver's extant letters are concerned with domestic matters-marriageof Richard.

Why does so large a proportion of Smith's extant letters consist of letters of introduction?

The thirteen extant letters of Plato.

One of the earliest extant letters of Michelangelo, written from Rome in 1497 to his brother Buonarroto, reveals a vivid interest in Savonarola.

And, fortunately for us, the most rapid evolution in his thought took place daring the ten years to which his extant letters belong.

This we know from the first of his extant letters, which is dated July 2, and addressed to Lorenzo di Pierfrancesco de' Medici.

Not only are his own extant letters during this period unusually few, but allusions to him in contemporary English correspondences are almost entirely absent.

Hardly anything is said in the extant letters of his marriage to Fanny Palmer, daughter of the Attorney-General of Bermuda, which took place in 1807.

I say "may have heard," because not a word is to be found in his extant letters about the concerts of these societies.