Instructions: In this task, you're given a sentence and your task is to generate a simplified sentence that focuses on lexical paraphrasing from the original sentence given in the input.
Input: progress in developing the tar was hindered by political and economic obstacles throughout the 1960s , 1970s and early 1980s.
Output:
political and economic obstacles hindered the tar 's developmental progress throughout the 1960 's , 1970 's and early 1980 's.