which should not be included as a heading in a chronological resume?

Which? Are you given choices?

Be sure to indicate what YOU THINK the correct choice is?

http://jobsearch.about.com/od/resumes/p/resumetypes.htm

In a chronological resume, it is important to include relevant headings that highlight your skills, experience, and qualifications in a clear and organized manner. While there may not be a definitive list of headings that should never be included, some headings may not be appropriate or necessary for a chronological resume. Here are a few examples:

1. Personal Information: In most cases, it is not recommended to include personal information such as your date of birth, marital status, or social security number. These details are often considered irrelevant or inappropriate for a professional resume.

2. Hobbies and Interests: While showcasing your hobbies and interests can be useful in some situations, such as when relevant to the position you're applying for, it generally does not add significant value to a chronological resume. Hiring managers are more interested in your qualifications and experience.

3. References: Including a separate heading for references is not necessary in a chronological resume. Instead, it is common practice to state "References available upon request" or simply omit this section altogether. If employers are interested in contacting your references, they will request them separately.

Remember, the structure and content of a resume may vary depending on the specific industry, job requirements, and personal circumstances. It's important to tailor your resume to align with the expectations of the employer or industry you're targeting.