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3. ‘Traffic Signs Manual Introduction’ 1982.Available athttps://www.gov.uk/government/uploads/system/uploads/attachment_data/file/203662/traffic‐signs‐manual‐chapter‐01.pdf
4. ‘California Drivers’ Handbook – Traffic Signs’ 2018.Available athttps://www.dmv.ca.gov/web/eng_pdf/dl600.pdf
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