There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
yasse
adverb. there [yonder]; once upon a time, once upon a time; there [yonder]
yasse tintilar i eleni
*wherein the stars tremble
yassen elli atintillinar
*wherein the stars tremble
elli yas atintilar
*wherein the stars tremble
ya
pronoun. remote demonstrative
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
A correlative appearing in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/97, 111), a combination of ᴹQ. ya “yonder” and the locative suffix ᴹQ. -sse. In The Etymologies of the 1930s, it was based on ᴹQ. yá “ago” and translated as “once upon a time” (Ety/YA). In Tolkien’s later writings, ya was a relative pronoun and not a demonstrative, but was still connected with the past and so might still mean “once upon a time”.