for Omega being non empty set
for Sigma being SigmaField of Omega
for P being Probability of Sigma
for BSeq being SetSequence of Omega st ( for n being Element of NAT holds BSeq . n is thin of P ) holds
ex CSeq being SetSequence of Sigma st
for n being Element of NAT holds
( BSeq . n c= CSeq . n & P . (CSeq . n) = 0 )