The second rule for using a semi-colon is to separate items in a list when there is already punctuation. For example: There are a number of cities that already suffer from the problems of overcrowding, such as Mexico City, Mexico; Dhaka, Pakistan; and Lagos, Nigeria. Because there are commas between the city and the country, we need to separate the list with semi-colons. This is particularly useful when writing about dates. For example: The graph peaked in November, 2005; April, 2006; and again in December 2006.