Complex sentence: On April 27, the group had managed to reach latitude 88 50', however bad ice conditions endangered their safety and they had to be evacuated and brought back to the Borneo drifting station.
Split into simpler sentences: On April 27, the group had managed to reach latitude 88 50 ′. However, bad ice conditions endangered their safety and they had to be evacuated and brought back to the Borneo drifting station.