... DE 951990. 1954. View all references 5d11. Heinrich , P. and Matthias , S. Production of compounds of the pyrimidine series. US 2778821. 1955. ... DE 951990 . 1954. 11. Heinrich, P. and Matthias, S. Production of compounds of the pyrimidine series. US 2778821 . 1955. 12. ...