Referral to hospital by general practitioners.
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005194:Family Practice; D005260:Female; D006760:Hospitalization; D006801:Humans; D008131:London; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D010817:Physician-Patient Relations; D012017:Referral and Consultation; D012737:Sex Factors