Complex sentence: The Federal structure, or some semblance of it, existed between 1952-09-15 and 1962-11-14 when it was officially dissolved and Eritrea was annexed by Ethiopia.
Split into simpler sentences: The Federal structure, or some semblance of it, existed between 1952-09-15 and 1962-11-14. On 1962-11-14 the Federation was officially dissolved and Eritrea was annexed by Ethiopia.