RNA-seq was first introduced in:
The concept of massively parallel cDNA sequencing for transcriptome profiling, now called RNA-seq, was demonstrated in pioneering studies published in 2008. Groups led by Wold, Grimmond and others used Illumina Genome Analyzer and 454 platforms to sequence yeast, mouse and human transcriptomes, showing superior dynamic range compared to microarrays for expression quantification and discovery of novel transcripts. The technology became feasible only after next-generation sequencers became robust. 2005 corresponds to early 454 sequencing, while 2010 and 2012 marked expansion into stranded, single-cell and long-read RNA-seq applications.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.