I have a study that we are examining. The sample was selected by sending the information about the study to the Korean Hospital Nurses Association.

I have a study that we are examining. The sample was selected by sending the information about the study to the Korean Hospital Nurses Association. From this the researchers obtained volunteers, they used 6 hospitals and a number of nurses and patients to complete the study. The mention of the sampling method is not noted. What type of sampling method would this be considered? I believe it is convenience sampling but want to make sure.