NMR study of urea-formaldehyde-ammonia oligomersSiimer, Kadri; Oja, Holger; Laht, AareKemia-kemi = [Finnish chemistry]1991 / p. 984-985 https://www.ester.ee/record=b1201067*est

Relationship between the chemical structure of urea-formaldehyde resins and properties of particleboardsLasn, Ilmar; Peterson, Aleksander; Laht, Aare; Siimer, KadriAbstracts of Nordic Polymer Days, Stockholm, 2-4 June 19931993 / p. 14