I want to know the answer to the following question:
Who has defined a period of when the post-punk era was?
All the background I'm provided with is that "Generally, post-punk music is defined as music that emerged from the cultural milieu of punk rock in the late 1970s, although many groups now categorized as post-punk were initially subsumed under the broad umbrella of punk or new wave music, only becoming differentiated as the terms came to signify more narrow styles.". Is that enough to answer the question?