Complex sentence: Albert Girard was the first to make the observation, describing all positive integral numbers (not necessarily primes) expressible as the sum of two squares of positive integers; this was published posthumously in 1634.
Split into simpler sentences: Albert Girard was the first to make the observation. Actually he made the determination of the positive integral numbers (not necessarily primes) expressible as the sum of two squares of integers; this was published posthumously in 1634.