Citation has its roots in the Latin word for 'cito', meaning appealing to something. It can be used to illustrate issues and to justify one's own opinions in a consistent manner.
According to § 22 of the Copyright Act, it is permissible to use citation from disseminated works to the extent required by the specific purpose and in accordance with fair practice . A separate permission from the author is not necessary. A work is considered disseminated when it has been made available to the public with the author's permission. The manner, in which the work is made public, is not significant.
According to the Copyright Act, the author's name and the source must be stated to the extent and in the manner required by fair practice. This principle must be adhered to when using a work on the basis of the provisions on quotations.  In practice, the manner of citing sources varies from field to field. Be consistent and remember to reference all the sources in an appropriate manner.
The maximum or minimum length of citation has not been precisely defined. In principle, it is possible to violate the copyright holder's exclusive rights with both, too long and too short quotations. In most cases, however, the problem is a citation that is too long. A work can never consist of citations alone; in this case permission would be required from the authors of all the copyrighted works. Similarly, it is not permissible to cite an entire work. The citation must always have a relevant connection to the work of the person citing, i.e. facilitate that person in their own creative work. The extent of permissible quotation may vary depending on the discipline in question. For Example The Copyright Council has accepted what comes to audiovisual works solely very short glimpses, of a few seconds, from a film. In The Copyright Council’s case 2002:16 that concerned quoting material from one 3 minutes long documentary videofilm for educational purposes could not be seen as a quotational use of footage and thus permissible or in accordance with the provision on the right to quote but required the author's or the copyright holder's permission.
Writers of articles published in scientific journals may need long citations in critiquing and commenting other authors' works and in justifying their own opinions. Ultimately, the extent of permissible citation is determined by the purpose, aims and context of its use.
The fair practice of citation has been considered to require using the citation to aid intellectual creative work. Thus, citations must be appropriately connected to the work of the citing party. In addition, there must be a justifiable reason for using a citation in the context it is presented in. Acceptable use of citations includes, among other things, providing support for your own thoughts and views and citing for illustrative purposes. 
On the basis of the restriction on citation (Section 25 of the Copyright Act), an image such as an illustration, a photograph or a photograph of an artwork may be used in connection with a scientific presentation. These images can be, and should be used as a whole work of art or as a whole photograph. The text of the presentation must be the main subject matter of critical or scientific article. Images must be related to the text; they must illustrate and clarify the text. Scientific presentations, for example theses, dissertation and course papers, are regarded as presentations that meet the general requirements for the scientific treatment of subject matter. Theses, dissertation and course papers may be distributed and shared in their entirety together with images on the Internet. However, it should be noted that if an agreement has been made on the use of an image, the nature and extent of such rights are defined by that agreement. For example if a student has been given a permission in an agreement to use an image from an archive solely in an analogue publication, the student is obliged to act accordingly. Therefore, it is advisable to reach an agreement that allows the use of copyright work in the digital university repository.
The right of attribution requires that the name of the author is mentioned in accordance with good practice. It is necessary to mention all the authors of the cited work. For example a photograph made of a work of design requires that both the name of the author of the work of design and the photographer are mentioned. In the case the photographer rests unknown it is recommended to mention the author in a following manner: Photographer unknown, source Archive x. However, different archives may have various prerequisites for mentioning it as a source. One should note that citing a copyrighted work does not give the status of a copyright owner neither to the student nor to the university, citing merely gives a limited right to use.
T. Leinonen, T. Toikkanen, and K. Silfvast, "Software as hypothesis: Research-based design methodology," in The proceedings of Participatory Design Conference 2008. ACM, 2008.
Notes and References
 Harenko, K., Niiranen, V., Tarkela, P., 2006. Tekijänoikeus - Kommentaari ja käsikirja. pp. 172 - 181
 Copyright Act