Complex sentence: The List of diplomats of Norway to China began when diplomatic relations were established since 1851, when the union between Norway and Sweden was existed at that time, a Norwegian-Swedish Consulate General was established in Guangzhou.
Split into simpler sentences: The List of diplomats of Norway to China began when diplomatic relations were established in 1851. The establishment of diplomatic relations took place during the union between Norway and Sweden, and a Norwegian-Swedish Consulate General was established in Guangzhou.