I am having trouble identifying the sampling design used in this study. "Transplant recipients living in a Midwestern metropolitan area were recruited through clinician referral, direct mailings from patient advocacy groups, and brochures placed in outpatient clinics and pharmacies. Inclusion criteria were a function- ing solid-organ transplant (ie, kidney, kidney/pancreas, pancreas, lung, liver, heart, or heart-lung), age 18 years or older, ability to read and write English, and willingness to attend classes. To avoid the confounding effects of surgical recovery, patients were at least 6 months posttransplant. Exclusions were being medically unstable or on dialysis, having serious preexisting mental health issues, or having previously practiced MBSR." Any help will be greatly appreciated!