Title: Aromatic plants of tropical Central Africa. XLVIII. Comparative study of the essential oils of four <i>Hyptis</i> species from Cameroon: <i>H. lanceolata</i> Poit., <i>H. pectinata</i> (L.) Poit., <i>H. spicigera</i> Lam. and <i>H. suaveolens</i> Poit.