U4 snRNA
Zwieb, C (1997). “The uRNA database”. Nucleic Acids Res 25 (1): 102–103. doi:10.1093/nar/25.1.102. PMC 146409. PMID 9016512. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC146409/.
Thomas, J; Lea K; Zucker-Aprison E; Blumenthal T (1990). “The spliceosomal snRNAs of Caenorhabditis elegans”. Nucleic Acids Res 18 (9): 2633–2642. doi:10.1093/nar/18.9.2633. PMC 330746. PMID 2339054. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC330746/.