- send us an email at info@htcc5.org (highly preferred),
- give us a ring at +385 1 4571203 (think of the time zones),
- contact us via social networks Facebook, Twitter or Instagram (so cool), or
- send us an old-fashioned letter to: Hrvatska udruga kristalografa (for HTCC5), Bijenička 54, HR-10000 Zagreb, Croatia (we shall be absolutely charmed but take the time factor into account before deciding to do so).