00386nas a2200133   4500000000100000008004100001100001600042700002100058700001400079700001300093700002100106245010500127250002000232       2013                            d1 aFerreira P.1 aBeckenkamp Paula1 aHopper J.1 aMaher C.1 aFerreira Manuela00aNature or nurture in low back pain? Results of a systematic review of studies based on twin samples.  a20 January 2013