- invert: vt. 1.翻过来，(上下、前后)倒 ...
- center: n. 1.中心；中心点；圆心；中央； ...
- and or invert gate: 与或非门; 与或非
- The collector ' s heart stood still as he saw that the sheet while been offered him had inverted centers
- The collector ' s heart stood still as he saw that the sheet , which had been offered him , had inverted centers
- Excited by his find , obey shopped other branch post offices for more sheets with inverted centers but found none
- Excited by his find , robey shopped other branch post office for more sheets with inverted centers but found none