Brahma Sutras
ॐ सर्ववेदान्तप्रत्ययं चोदनाद्यविशेषात् ॐ ॥ ३-३-१॥
Any (particular) conception for meditation (vijnana) imparted in all the Upanishads is the same on account of the sameness of the injunction etc.
english translation
OM sarvavedAntapratyayaM codanAdyavizeSAt OM ॥ 3-3-1॥
hk transliteration by Sanscript