Complex sentence: He continued to send most of his work to Crelles Journal., but summer 1828 he published, in rivalry with C.G.J.Jacobi, an important work on elliptic functions in Astronomische Nachrichten in Altona.
Split into simpler sentences: He continued to send most of his work to Crelles Journal. But in the summer of 1828 he published, in rivalry with C.G.J.Jacobi, an important work on elliptic functions in Astronomische Nachrichten in Altona.