 Complete the following phrase:  The round of 16 ties were to be played across four weeks, with the first legs being played across two weeks in February and the second legs across two weeks in March. Because of this, the first leg ties were unaffected by the pandemic, but the second leg ties were affected in different ways. All of the four matches in the first week of fixtures went ahead but due to the increased severity of the COVID-19 pandemic in Spain and France, Valencias and PSGs home games were played behind closed doors. On 15 March, UEFA announced a halt to the competition meaning that the remaining second leg games would be postponed indefinitely. A taskforce was convened to reschedule the rest of the season. On 23 March, it was announced that the Atatürk Olympic Stadium in Istanbul, Turkey would no longer host the 