Thirty-four years of pollen monitoring: an evaluation of the temporal variation of pollen seasons in Belgium, Hoebeke, Lucie, Bruffaerts Nicolas, Verstraeten Caroline, Delcloo Andy, De Smedt Tom, Packeu Ann, Detandt Monique, and Hendrickx Marijke , Aerobiologia, 2018 June, Volume 34, Issue 2, Number 155, (2018)