If you need "after hours" emergency veterinary assistance:

You may LOOK in the Yellow Pages under "Veterinarians" or other likely headings in the same part of the Yellow Pages: for example, Veterinary Emergency Services, etc.

Some veterinary clinics/hospitals offer 24-hour emergency services.

You may try looking-up a veterinarian under his/her name in the White Pages.

Or, search the Internet for veterinary clinics/hospitals or a particular veterinarian at google.com or anywho.com.