Northern Cities shift as a vowel chart, based on image in Labov, Ash and Boberg (1997), "A national map of the regional dialects of American English" at [1], retrieved 10.04.2010.
California_English_vowel_chart.svg
California_English_vowel_chart.svg: *California_English_vowel_chart.png: Angr
IPA_vowel_trapezium.svg: (talk)
derivative work: Moxfyre (talk)
derivative work: Cassowary (talk)