CCEO c. 570
Particular law can establish other kinds of ascetics who imitate eremitical life, belonging or not to an institute of consecrated life. Consecrated virgins and widows who live on their own in the world, having publicly professed chastity, can also come under norms of particular law.
Exegetical Analysis of CCEO c. 570 
Estudio canonico sobre la viudez consagrada
Christina Hip-Flores, JCD 