Complex sentence: Stone was the Washington, D.C., correspondent for "PM", and published a series of feature articles about the Jewish European refugees who ran the British blockade to reach Palestine; afterwards, Stone developed that reportage and wrote the book "Underground to Palestine".
Split into simpler sentences: Stone was the Washington, D.C., correspondent for "PM", and published a series of feature articles about the Jewish European refugees who ran the British blockade to reach Palestine. Stone later developed further that reportage and wrote the book "Underground to Palestine".