Original sentence: During the 20th century, several attempts at negotiations were made, with various tradeoffs under consideration: according to one proposal, Iran would recognise Arab ownership of Abu Musa in return for the emirates recognising Iranian ownership of the Tunb Islands; according to others, one side would lease or sell the Tunb Islands to the other.From 7 June 1921 until 30 November 1971 the islands were administered by the shaikh of Ras al-Khaimah.In the period from 17 June 1904 until the recognition of Ras al-Khaimah as a separate shaikhdom by Britain on 7 June 1921, the Tonbs remained under the administration of the shaikh of Sharjah
Edited sentence: During the 20th century, several attempts at negotiations were made, with various tradeoffs under consideration: according to one proposal, Iran would recognise Arab ownership of Abu Musa in return for the emirates recognizing Iranian ownership of the Tunb Islands; according to others, one side would lease or sell the Tunb Islands to the other