• Condensation of methylolphenolsChristjanson, Peep; Köösel, Arne-Enn; Suurpere, AimeOil shale1999 / 4, p. 369-376: ill https://artiklid.elnet.ee/record=b1002756*est
• Condensation of methylolphenolsChristjanson, Peep; Köösel, Arne-EnnXII. Sympozium Pokroky vo vyrobe a použiti lepidiel v drevarskom priemysle : zbornik referatov / Technicka univerzita Zvolen1995 / p. 298-309: ill