Always compare the PDF instructions with a teacher (Guru) or senior practitioner, as Vedic rituals often have regional variations.
The book referred to as Yagnik Ratnam is typically a commemorative volume or a biography detailing his life, philosophy, and letters. In some contexts, it is a compilation of his own writings; in others, it is a festschrift (a collection of writings honoring a scholar) published by his peers. yagnik ratnam book pdf
While not the same, you can find excellent, legally available PDFs of "Rig Vidhana" or "The Taittiriya Aranyaka" on Archive.org and SanskritDocuments.org . These contain 90% of the mantras used in fire rituals. Always compare the PDF instructions with a teacher