https://plato.stanford.edu/entries/nagarjuna/
"The central concept around which all of Nāgārjuna’s philosophy is built is the notion of emptiness (śūnyatā). Emptiness is of course always the emptiness of something, and the something Nāgārjuna has in mind here is svabhāva. Different terms have been used to translate this word into English: “inherent existence” and “intrinsic nature” appear to be the more popular choices, but “substance” and “essence” have also been proposed. None of these cover the full complexity of the term, however. We therefore have to give some more detailed account of the way svabhāva is characterized in Nāgārjuna’s thought. By understanding what empty things are supposed to be empty of we simultaneously gain a more precise understanding of the concept of emptiness."
https://plato.stanford.edu/entries/laozi/
"Philosophical Daoism traces its origins to Laozi, an extraordinary thinker who flourished during the sixth century B.C.E., according to Chinese sources. According to some modern scholars, however, Laozi is entirely legendary; there was never a historical Laozi. In religious Daoism, Laozi is revered as a supreme deity."
https://plato.stanford.edu/entries/confucius/
"Many of the short passages from the Analects, and the “Thicket of Sayings” passages excavated at Guodian, describe the development of set of ideal behaviors associated with the moral ideal of the “way” (dao 道) of the “gentleman” (junzi 君子). Based on the analogy between the way of Confucius and character ethics systems deriving from Aristotle, these patterns of behavior are today often described using the Latinate term “virtue”. In the second passage in the Analects, the disciple You Ruo 有若 says a person who behaves with filial piety to parents and siblings (xiao and di 弟), and who avoids going against superiors, will rarely disorder society. It relates this correlation to a more general picture of how patterns of good behavior effectively open up the possibility of following the way of the gentleman: “The gentleman works at the roots. Once the roots are established, the way comes to life” (1.2). The way of the gentleman is a distillation of the exemplary behaviors of the selfless culture heroes of the past, and is available to all who are willing to “work at the roots”. In this way, the virtues that Confucius taught were not original to him, but represented his adaptations of existing cultural ideals, to which he continually returned in order to clarify their proper expressions in different situations. Five behaviors of the gentleman most central to the Analects are benevolence (ren 仁), righteousness (yi 義), ritual propriety (li 禮), wisdom (zhi 智), and trustworthiness (xin 信)."
https://www.britannica.com/topic/Zen
An entry in the Encyclopedia Britannica on Zen Buddhism.
https://www.britannica.com/topic/sunyata
http://www.buddhanet.net/cbp2_f6.htm
Articles on emptiness.