What is the concept of 华夏? This paper talks about the concept of 华夏:

At the core of this traditional Chinese identity is the concept of hua-hsia. By invoking a sense of Chineseness (hua) that is rooted in the shared civilization of the first (mythical) dynasty (hsia), hua-hsia is, in essence, a code word for both political legitimacy and historical destiny.

It does explain it slightly above but it doesn't really go into detail. Dictionaries just mention words like &quot;China,&quot; &quot;Cathay&quot; and even &quot;Han.&quot;
What further concepts are linked to 华夏, as mentioned in the quote above?
According to the Chinese language wiki, the word 华夏 is just an Ancient word for 夏人, or the people of the Xia dynasty.

夏朝在上古為中央大國[2]，但“夏人”一般是指夏朝遺民[3]。而“華夏”僅為漢朝之前的代名詞[4]


In Early Old Chinese, the Xia dynasty was the central power, but &quot;夏人&quot; was generally used to refer to the descendants of the Xia dynasty. &quot;華夏&quot; is simply a synonym that was used before the Han dynasty.

The text goes on to explain that in the early Qin dynasty it was used to also classify people in the Zhou dynasty. It looks like this is an example of using the word to affirm political legitimacy-- they used this terminology to affirm that anyone who followed Zhou Li of the Zhou dynasty was a descendant of the even older (and therefore more legitimate?) Xia dynasty by saying they were 華夏, but that people who did not follow Zhou Li were barbarians, even if they belonged to the Zhou family.

在先秦時代，華夏僅為周王朝的代稱[8]，同時凡遵周禮、守义之諸侯國人，也稱為華人、夏人，通稱為諸華、諸夏，不遵守周禮、不尊重周天子、非周「王母弟甥舅」的諸侯國則被視為「蠻夷戎狄」[9][10]，縱使是周王族的吳國，不守周禮[11]及稱王的舉動，一樣被視為「蠻夷戎狄」。

This article does note that some historians believe that in Early Old Chinese &quot;Hua&quot; and &quot;Xia&quot; were pronounced the same, and originally just one character. They also give an example in the Zuo Zhuan where the two are interchangeable.

一些歷史學家認為華、夏兩字上古同音，本一字。《左傳》“裔不謀夏，夷不亂華”一語，華、夏同義反復，華即是夏。

Tl;DR If the paper you are using predates the Han dynasty, it's possible that it is saying this word with purpose, to intentionally claim a longer and more honorable lineage for the group of people it is referring to, but if it was written after the Han dynasty the word choice was probably just for style as at that point the word is interchangeable with 华人.