https://doi.org/10.1016/s0076-6879(02)38215-6 Cross-Correlated Relaxation for Measurement of Angles between Tensorial Interactions H Schwalbe, T Carlomagno, M Hennig, J Junker, B Reif, C Richter & C Griesinger Methods in Enzymology 338, 35–81 (2001)