The problem was solved simply by using an already standard character that had a similar sound to what the Viet called themselves.
( ( The problem ) ( ( was ( ( solved simply ) ( by ( using ( ( an ( already ( standard character ) ) ) ( that ( had ( ( a ( similar sound ) ) ( ( to what ) ( ( the Viet ) ( called themselves ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN problem)) (VP (VBD was) (VP (VBN solved) (ADVP (RB simply)) (PP (IN by) (S (VP (VBG using) (NP (NP (DT an) (RB already) (JJ standard) (NN character)) (SBAR (WHNP (WDT that)) (S (VP (VBD had) (NP (NP (DT a) (JJ similar) (NN sound)) (SBAR (WHPP (TO to) (WHNP (WP what))) (S (NP (DT the) (NNP Viet)) (VP (VBD called) (NP (PRP themselves))))))))))))))) (. .)))
The problem remained intractable because it was impossible to substitute other characters.
( ( The problem ) ( ( ( remained intractable ) ( because ( it ( was ( impossible ( to ( substitute ( other characters ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN problem)) (VP (VBD remained) (ADJP (JJ intractable)) (SBAR (IN because) (S (NP (PRP it)) (VP (VBD was) (ADJP (JJ impossible) (S (VP (TO to) (VP (VB substitute) (NP (JJ other) (NNS characters)))))))))) (. .)))