Proc Natl Acad Sci U S A. 1972 Oct;69(10):3009-13.

Silber R, Malathi VG, Hurwitz J.

Purification and properties of bacteriophage T4-induced RNA ligase.

0.1 mM PPi inhibits RNL1. Polypurines concatenate better than polypyrimidines. Primary paper for the RNA ligase assay.