"The name 'Véda' is given to the Mántra and the Brā́hmaṇa."
Ádhi-Dāivam áth' ā́dhy-ātmam
ádhi-yajñam íti trayám
Mántreṣu Brā́hmaṇe c' āivá
Şrutám íty ábhi dhīyate.
"The three-fold knowledge pertaining to the Gods, the soul, and the sacrifice, found in the Mántra-s and in the Brā́hmaṇa, is considered the Şrutá (Véda)."
Are the Āraṇyaká-s and the Upaniṣád-s part of the Véda? If so, then why did Āpastamba not mention it in his şrāuta-sūtrá as part of the Véda? Why are Āraṇyaká-s and the Upaniṣád-s not found under the definition of Şrutá (Véda)?
References from the Véda (obviously not from the Āraṇyaká-s and the Upaniṣád-s) itself is preferred.