This article is from the Mongolia FAQ, by Oliver Corff with numerous contributions by others.
Zanabazar created a second writing system which looks very much like a
horizontal version of the Phagsba script, and indeed it shares the
same Tibetan roots. Horizontal Square Writing has a close resemblance
to many Tibetan characters, and similar to the Soyombo alphabet, it
shows the same typical arrangement of short and long vowels, together
with basically the same order of consonants.
Only a few documents in Horizontal Square Writing have survived, and
the script was never popularized.
 
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