  The formation of low emission lines in quasars and active galactic nuclei is
still an open issue. Aided by the organizing power of the 4D eigenvector 1
scheme, we review basic developments since the 1980s, devoting special
attention to the CaII IR triplet and the OI 8446 emission lines. Coverage of
these lines is cumbersome since they are shifted in an inconvenient IR domain
already at modest redshifts (~ 0.2). Their detection is also difficult since
they are faint and often buried in the Ca II absorption of the host galaxy. We
discuss how these lines can provide unambiguous constraints on the physical
conditions of the broad line emitting regions of quasars when detected in
emission, and summarise preliminary results for a sample of luminous,
intermediate redshift quasars.
