Citation Style Guide

The American Society of Mechanical Engineers (ASME) offers some of the engineering profession’s most esteemed publications in the field of mechanical engineering. 

Note: ASME primarily uses a form of the Chicago Manual of Style for reference format. Authors are encouraged to seek out precise instructions through the Chicago Manual of Style.

The Council of Science Editors (CSE) is an international membership organization for editorial professionals publishing in the sciences. CSE Style offers three systems of documentation: 

1. Citation-sequence: Citations are included in a numbered list at the end of the paper, in the order in which they appear in the text. Within the text of your paper, use superscript numbers to refer to the corresponding citation in your citation list. 
2. Citation-name: Citations are included in a numbered list at the end of the paper in a numbered list, in alphabetical order by author last name. Within the text of your paper, use superscript numbers to refer to the corresponding citation in your list. 
3. Name-year: Citations are listed at the end of the paper in alphabetical order by author last name, but not numbered. Within the text of your paper, cite sources by using the author's last name followed by the year of publication in parentheses. For example: Jones (2005). 
4. In all three systems, a reference list at the end of the paper provides all the information your reader needs to track down your sources. 

The Institute for Electrical and Electronics Engineers (IEEE) is a professional organization supporting many branches of engineering, computer science, and information technology.

• In addition to publishing journals, magazines, and conference proceedings, IEEE also makes many standards for a wide variety of industries.
• IEEE citation style includes in-text citations, numbered in square brackets, which refer to the full citation listed in the reference list at the end of the paper.
• The reference list is organized numerically, not alphabetically. For examples, see the IEEE Editorial Style Manual. 

According to Harvard Library, the "Harvard System" is something of a misnomer, as there is no official institutional connection.

It's another name for the author/date citation system, the custom of using author and date in parentheses, e.g. (Robbins 1987) to refer readers to the full bibliographic citations in appended bibliographies.