Why does it show an error please solve

CREATE TABLE Staff ( S.NO NUMBER(5) PRIMARY KEY, Se Name VARCHAR(15) NOT NULL, Position VARCHAR(15) NOT NULL ) CREATE TABLE Census..tcast Icast.NO MLIMBER (5) PRIMARY KEY, Geographical boundary VARCHAR(10) NOT NULL, Median.Housebold. Income MEMBER (5) NOT NULL, Iocoue. Rer Sanita NUMBER (5) NOT NULL, Median Renter Income NUMBER(S) NOT NULL, | Income. Dercapita.gCOUR MURER (5) NOT NULL, Median Rer Rental NUMBER(5) NOT NULL, Median. GcassRent, MUMBER (5) NOT NULL, Percentage Income FLOAT(5) NOT NULL ALTER TABLE Owner ADD FOREIGN KEY (S.NO) REFERENCES Staff (S.NO) ORA-00904: "S_NO": invalid identifier ALTER TABLE CEOsustcact FOREIGN KEY (5.NO) REFERENCES Staff(.NO) ORA-01735: invalid ALTER TABLE option ALTER TABLE Elected Official ADD FOREIGN KEY (tract.N) REFERENCES Sensus.tracticast.no) ORA-00904: "TRACT_NO": invalid identifier