In-Text Citations
This document explains and exemplifies appropriate citation and referencing in an
academic paper. Examples are taken from Mark Kupets, “Inferring Mixtures of Markov
Chains.” Senior Design Report, University of Pennsylvania School of Engineering, CIS,
April 2005. Some citation examples are modified.
Appropriate use of another source. In this example, the author weaves mention of the
source into the opening sentence of the paragraph by stating the names of the authors, the
title of the published source, and date of publication. (A matching entry in the List of
References gives the reader full citation information for the published paper.)
This project is based directly on the work of Batu, Guha, and Kannan as
published in “Inferring Mixtures of Markov Chains” [1]. In that paper, the
authors present algorithms for “inferring Markov chains from a stream of
interleaved behavior”. The authors give results for various versions of the
inference problem, including where the Markov chains have pairwisedisjoint state sets, in both the simple and chain-dependent mixture models,
and when the Markov chains have non-disjoint state sets.
Introduction of a paragraph-length paraphrase or quote. When the author is
paraphrasing a long passage from the source, he credits the source at the beginning. Since
he has mentioned the source earlier, now he can refer to it as “Batu et al.[1].” The form
is, First author et al. [reference number]. Note: the expression et al. is Latin. The word
alia is abbreviated to al. and is followed by a period. It’s customary to italicize the
expression (and doing so will keep Microsoft Word from interpreting it as the end of a
sentence if it is not).
The following is a description of the problem that this project addresses as
set forth by Batu et al. [1].
Consider a state space of Markov chains …..
Use of material from multiple sources, with credit at the end of the text. When the
focus is on material discussed in many sources, it’s appropriate to list the sources at the
end of the discussion, as in the following example. Each source is listed by reference
number.
A discrete-time Markov chain consists of a set of states and a transition
matrix that specifies the probability of going to some next state, y, given
only the current state x …. [2,3,4].
Choice of verb tense: In most cases, use present tense when referring to published
work. See the first example above. Here is another example:
Zeboulon, Bennani & Benadbeslem [5] study applying the “’EM’
algorithm to deduce the initial parameters of a Markov chain mixture
model dealing with navigation sessions on a website….” [This result] is
related to the project, but also deals with one Markov chain, rather than a
mixture of them….
The use of past tense is appropriate if the focus is to give a historical overview, as in the
next example.
Batu, Guha and Kannan [1] defined the problem of “inferring a ‘mixture
of Markov chains’ based on observing a stream of interleaved outputs
from these chains,” and gave algorithms for solving various versions of
the problem.
Quoting versus paraphrasing. Note in the above examples that words from the cited
authors are woven into the text in the form of quotes. Use discretion when choosing to
quote rather than paraphrase. Only quote if the words you are quoting are uniquely
expressive. Avoid letting the cited authors write your paper. Instead, rephrase general
content into your own words:
Misused quote: While some research has been done in the area of
inferring Markov chains, hidden Markov chains, and other related areas,
“To the best of our knowledge, mixture models of Markov chains have not
been explored” [1]. 
Paraphrase: Some research has been done in inferring Markov chains,
hidden Markov chains, and other related areas. However, as Batu et al.
point out [1], models mixing types of Markov chains have not been
explored.
The List of References. The List of References at the end of your paper must contain
every work that was cited in the paper, and only those works cited in the paper. Use the
same system in the List of References that you use to create citations within the paper
(that is, if citations are in ACM style, the list of references should also be in ACM.)
[1] Batu, T., Guha, S., & Kannan, S. 2004 Inferring Mixtures of Markov Chains. COLT,
(Sept. 2004) 186-199. http://www.cs.sfu.ca/~batu/personal/papers/mcmix.pdf.
[2] Black, P. E. 2005. Markov Chain. National Institute of Standards and Technology
(Jan. 2005).
[3] Khamsi, M. S. 2005. Markov Chains. S.O.S. Mathematics. (April, 2005)
[4] Weisstein, E. 2005. Markov Chain. MathWorld. Wolfram Research. (April, 2005)
[5] Zeboulon, A., Bennani, Y., & Benadbeslem, K. 2003. Hybrid connectionist approach
for knowledge discovery from Web navigation patterns. Book of Abstracts.
ACS/IEEE International Conference on Computer Systems and Applications (1418 July 2003) ,118. DOI=http://dx.doi.org/10.1109/AICCSA.2003.1227550
Use of footnotes. A footnote is a note at the bottom of a text page. The reader sees a
superscript numeral in the text of the paper, and looks at the bottom of the same page for
the footnote with that number. In modern editorial style, footnotes are not used for
citation information. Use footnotes only for comments on the text, or for adding
background or explanatory information.
NOTE: Some guides still refer to citations or references as ‘footnotes’ or ‘endnotes.’ Do
not be confused by this usage. Citations belong in the text of the paper; references belong
at the end of the paper.
For more information and further examples:
ACM Style:
Latex:
http://www.acm.org/sigs/publications/sig-alternate.cls (style file)
http://www.acm.org/sigs/publications/sig-alternate.tex (example file using the sigalternate style)
MS Word:
http://www.acm.org/sigs/publications/pubform.doc