What is the late 1941 when 1978 veteran membership is 20000
{'header': ['! Late 1941', 'Late 1942', 'Sept. 1943', 'Late 1943', 'Late 1944', '1978 Veteran membership'], 'page_title': 'Yugoslav Partisans', 'section_title': 'Composition', 'caption': 'Composition', 'rows': [['Bosnia and Herzegovina', '20000', '60000', '89000', '108000', '100000'], ['Croatia', '7000', '48000', '78000', '122000', '150000'], ['Kosovo', '5000', '6000', '6000', '7000', '20000'], ['Macedonia', '1000', '2000', '10000', '7000', '66000'], ['Montenegro', '22000', '6000', '10000', '24000', '30000'], ['Serbia (proper)', '23000', '8000', '13000', '22000', '204000'], ['Slovenia', '2000', '4000', '6000', '34000', '38000'], ['Vojvodina', '1000', '1000', '3000', '5000', '40000']]}