Two recensions — Kṛṣṇa and Śukla
The Yajur Veda is unusual among the four Vedas for surviving in two significantly different textual traditions. The Kṛṣṇa (Black) Yajurveda mixes mantras with explanatory Brāhmaṇa-style prose directly within the Saṃhitā itself — giving it, in the tradition's own description, a "mixed" or less orderly character. Its best-preserved and most-studied recension is the Taittirīya Saṃhitā, organized into seven kāṇḍas (books) and 651 anuvākas. Other surviving Kṛṣṇa recensions include the Maitrāyaṇī, Kāṭhaka, and Kapiṣṭhala Saṃhitās.
The Śukla (White) Yajurveda keeps mantra and ritual explanation cleanly separated — the mantras form the Vājasaneyi Saṃhitā (named for Vājasaneya, a patronymic of the sage Yājñavalkya), while the explanatory material forms its own separate text, the Śatapatha Brāhmaṇa. Two recensions survive: Vājasaneyi Mādhyandina and Vājasaneyi Kāṇva.
The Śrī Rudram
Among the Yajur Veda's most significant liturgical contributions is the Śrī Rudram (also called the Rudra Praśna), found in the Taittirīya Saṃhitā (book 4, chapters 5 and 7) — a hymn consisting of the Namakam (a long litany of salutations to Rudra in his many forms and associations, each beginning namaḥ) and the Chamakam (a litany of requests). The phrase at the heart of the Pañcākṣarī mantra, Oṃ Namaḥ Śivāya, has its textual root here.
Mantras from the Yajur Veda tradition, in full
Several mantras and invocations in this codex's Mantras section are drawn from, or textually rooted in, the Yajur Veda and its associated Upaniṣads:
Associated Upaniṣads
More major Upaniṣads are attached to the Yajur Veda than to any other Veda. The Śukla recension carries the Īśāvāsya Upaniṣad (uniquely embedded directly within the Vājasaneyi Saṃhitā itself, rather than as a separate text) and the Bṛhadāraṇyaka Upaniṣad, the longest and one of the oldest of the major Upaniṣads. The Kṛṣṇa recension carries the Taittirīya, Kaṭha, Śvetāśvatara, and Maitrī Upaniṣads.
Michael Witzel, "Vedas and Upaniṣads," in The Blackwell Companion to Hinduism (ed. Flood, Blackwell, 2003). Patrick Olivelle, The Early Upaniṣads (Oxford University Press, 1998).