Please note that "harvard style" denotes a specific formatting style for citation call-outs, viz., author-year style citation call-outs. Harvard-style citation call-outs can be either 'text style' -- Jones (2017), generated via \citet -- or 'parenthetic style' -- (Jones, 2017), generated via \citep. Importantly, "harvard style" has exactly zero implications for the way the bibliographic entries are formatted in the bibliography section. [Aside: The term "harvard" citation style appears to have come about because it was first employed by a Harvard University professor for a scholarly paper published in 1881 [!]. Lots of people still call it "harvard style"; however, I think it's more descriptive to call this citation style "author-year" or "author-date" style.]
Let's examine an excerpt from one of your comments in more detail. With regard to the format of the citation call-outs, the instructions are that the citation call-outs should employ ...
... either ... the Harvard system, in which the names and dates [are] given in the body of the text and the references [are] alphabetically listed at the end of the report, or a system in which numbers are inserted in the text, ... e.g. [3].
I interpret this passage as implying that you have complete freedom to organize your citation call-outs using one of two, very different, formats: Either
"harvard style", with the entries in the formatted bibliography being sorted alphabetically by authors' names, or
"numeric style", viz., [1], [2], [3], etc.
Interestingly, there seem to be no stipulations whatsoever as to how the bibliographic entries should be formatted in the bibliography (other than that they must be sorted alphabetically by authors' names). E.g., article titles may or may not be encased in quote marks; journal names may or may not be rendered in italics; titles may employ either sentence style or title style; publication years could be shown either immediately after the authors' names, at the end of each entry, or anywhere inbetween; etc.
To preserve maximal flexibility, I recommend you use the natbib citation management package. (This package provides the commands \citet and \citep.) If you wish to employ "harvard" (or authoryear) style for the citation call-outs, I further suggest that you (a) load natbib with the option authoryear and (b) use either the plainnat or the abbrvnat bibliography style. If, on the other hand, you wish to go with the so-called "numeric" style for the citation call-outs, I suggest you load natbib with the option numbers and that you use the unsrtnat bibliography style; that way, the citation call-out numbers will be in ascending order in the body of the text. [Aside: You may well wonder what I mean by the term "maximal flexibility" in the context of bibliography styles. The bibliography styles plainnat, abbrvnat, and unsrtnat recognize and employ only a fairly basic set of bibliographic fields. Other, more recent, bibliography styles -- such as apacite -- recognize many more fields. The upshot is that if you organize your bib file so that it compiles correctly under plainnat, the odds are excellent that it will also compile correctly under a more elaborate bibliography style.]
Incidentally, whenever one changes the argument of \bibliographystyle, it is necessary to run a full recompile cycle -- LaTeX, BibTeX, and LaTeX twice more -- to fully propagate all changes.
natbiband an appropriate.bst, but we need to know more about the exact format you want. – Joseph Wright Nov 01 '17 at 12:40Either in the Harvard system, in which the names and dates given in the body of the text and the references to be alphabetically listed at the end of the report or a system in which numbers are inserted in the text, for e.g. [3]. In short, the references at the end of the report should be displayed in alphabetical order, following the Harvard style. Further, the citations included in the report should follow the numbered style. – M S Nov 01 '17 at 12:45abbrvnatofnatbibpackage. I betbiblatexhas a fitting counterpart. An even more unorthodox idea is to use a CSL style of a journal you aim for. See https://github.com/citation-style-language/styles .pandoccan take a CSL style and aBIBfile as an input and generate a proper citation list in the generated LaTeX, DOCX or whatever output. (Edit: see https://tex.stackexchange.com/a/146123/142180) – Oleg Lobachev Nov 01 '17 at 13:02