The phrase "a rather small part" is correct and usable in written English.
It can be used to describe a portion of something that is not large in size or significance.
Example: "In the grand scheme of the project, this is just a rather small part of what we need to accomplish."
Alternatives: "a relatively minor portion" or "a somewhat insignificant part".
So far, Web revenue is a rather small part of the broadcast networks' bottom lines, although Mr. Westin said ABC's digital income was "up substantially".
While it is understandable that our attention should be focused on Calais and Dover, this is a rather small part of the issue.
At the chosen spatial scale only a rather small part of the observed particularly high concentrations can be identified as anthropogenic anomalies and thus true soil contamination.
The deal includes a rather small part of the negotiating programme that was launched 12 years ago, known as the Doha Round.
Yet, the donations to charities and their injunctions form a rather small part of the zakah obligations constantly discharged by Muslims in their societies through personal and informal channels.
Worse yet, exons, protein coding sequences, turn out to be a rather small part of inheritance, even on the level of DNA.
And then on top of that, in a rather smaller part of ourselves, is an aspect of which we are conscious.
However, most of these studies were based on rather small parts of the species range or a rather restricted number of populations.
Bipolar illness, as the term is now used in the DSM-5 (Angst 2013), is not the same thing as MDI, but is rather smaller part of the latter.
A dedicated FMS is designed to produce a rather small family of similar parts with a known and limited variety of processing requirements, while in a random-type system, a large family of parts having a wide range of characteristics with random elements is produced and the product mix is not completely defined at the time of installing the system.
Although a rather small population of patients was part of the pilot study, the results are promising and should be studied in subsequent larger clinical trials: PDT followed by imiquimod treatment was well tolerated and combination of both improved the reduction of actinic keratoses, as demonstrated by the authors.
