1) The first successful portable MP3 player, the Diamond Rio PMP300, was released in 1998 and could hold up to 60 minutes of music.

2) The first modern Olympic marathon race was held at the 1896 Olympics in Athens and has since become one of the most iconic and challenging events in athletics.

3) The concept of proportional representation, used in some electoral systems, aims to ensure that political parties' representation in government aligns more closely with the proportion of votes they receive from the electorate.

4) The global response to climate change includes the Paris Agreement, an international treaty aiming to limit global warming and strengthen countries' efforts to address climate change through mitigation and adaptation strategies.