We are proud to announce that we have published Singularity proper! Please cite the Singularity software as:

Kurtzer GM, Sochat V, Bauer MW (2017) 
Singularity: Scientific containers for mobility of compute. 
PLoS ONE 12(5): e0177459. https://doi.org/10.1371/journal.pone.0177459

Woohoo!