Moore, Olin H. "The Romanticism of Guy de Maupassant." Publications of the Modern Language Association of America (1918): 96-134.
In Moore's article, Guy de Maupassant in particular is examined as an example of a prominent naturalistic author, whose reactions to Romanticism included a disdain for fantastic plots, making of their works "merely a series of scenes" (p. 96). Moore calls de Maupassant "the purest representative" of this naturalism. The author is shown to depict opposites and have thematic repetition in his stories; the falseness of the necklace in the story in question is contrasted with another story, les Bijoux, in which the jewels at the center of the story turn out to be genuine.
This source is an old analysis of de Maupassant's works, which was comparatively contemporaneous ("The Necklace" was only written approximately twenty years previous to this). The work appears in a reputable publication, the Publications of the Modern Language Association of America, and thus can be considered fairly valid as a piece of literary criticism. I believe that the information is extremely reliable, and provides an excellent bit of context for the rest of Guy de Maupassant's writing career.
This source was fairly helpful to me; while it says little of the actual short story itself, I do gain a much greater understanding of de Maupassant's style of writing, and the themes that he usually picks up on. His use of naturalism provides a great deal of context for the thematic material of "The Necklace," and I will argue that de Maupassant's consistent use of naturalism demonstrates that the class-related themes and plots of his works are meant to be part of a larger discussion on the differences between social and economic classes.
Supriyanto, Bambang. "Mathilde’s Internal and External Conflicts as Reflected in Guy De Maupassant’s The Necklace." Students' Journal of Language & Culture 1.11-68 (2012). In this source, the author describes the internal and external conflicts of the main character, Mathilde, as part of a series of class-related anxieties that she has. In essence, Mathilde wishes to look glamorous in order to elevate herself above the lower class means that she is capable of. Mathilde constantly struggles against the social conditions that she has to deal with, attempting to advance herself beyond her current means. However, in this effort she becomes more fully entrenched in the debt system.
As a source in my bibliography, its status as a published work is somewhat overshadowed by the fact that it is very much not written by a native English speaker - the poor use of English in the work ("The writer analyzes that Madame Mathilde is glamour a woman and responsibility person") throws their understanding of the language (and thus their ability to communicate their ideas) into question. Furthermore, the analysis of the internal and external conflicts in the work is not done with a great level of detail, so there is just a few surface elements to draw from. The source is from a students' journal, which possibly does not undergo a great deal of editing - otherwise, the quality of writing in this article may not have passed muster.
Despite the flaws in the article, however, I believe I can use it to good effect in my argument. The clear outlining of the internal and external conflicts of Mathilde during the story will allow me to have support for their establishment, as well as the presence of themes of class conflict and anxiety that are present in the work.
Shire, Kathryn. "Guy de Maupassant’s Characters and their Relationship to Animals." German Romanticism, the Sociology of Knowledge and Identity Crisis in Wolf’s Unter den Linden 48: 267.
In Shire's work, she discusses de Maupassant's relationship to naturalism, particularly in the characters' relationships to animals. In the case of "The Necklace," this naturalism is echoed in many elements of the story as outlined by Shire, including the suggestion of wearing flowers to the party, their comparison to "nocturnal animals," and more - all tied into the issues of class and social dignity that are explored in the work. Shire believes that de Maupassant wants to put humans and animals "on the same level," and as such compares them often in his works. This source is actually quite useful; though it is a piece of undergraduate thesis research, the work itself is well analyzed and researched, providing a great deal of connection to Moore's work as well. It is part of an anthology Journal of Undergraduate Research from the University of Michigan and Oakland University, and the author is a literature professor at the latter. Examining this naturalism through many of de Maupassant's works, the information appears to be fairly reliable, and will further support the points I wish to make in my argument about the story being related to class issues. The animal metaphors will also be helpful, as the comparison to 'nocturnal creatures' indicates lower class anxiety about being around the upper class.