###HUMAN: what is the name of procedure patient 51200 has been given two times last month?, ###ASSISTANT: SELECT d_icd_procedures.short_title FROM d_icd_procedures WHERE d_icd_procedures.icd9_code IN (SELECT t1.icd9_code FROM (SELECT procedures_icd.icd9_code, COUNT(procedures_icd.charttime) AS c1 FROM procedures_icd WHERE procedures_icd.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.subject_id = 51200) AND DATETIME(procedures_icd.charttime, 'start of month') = DATETIME(CURRENT_TIME(), 'start of month', '-1 month') GROUP BY procedures_icd.icd9_code) AS t1 WHERE t1.c1 = 2)