theorem Th36: :: CHAIN_1:39

for d being non zero Nat
for G being Grating of d
for A being Subset of (REAL d) holds
( A in cells (d,G) iff ex l, r being Element of REAL d st
( A = cell (l,r) & ( for i being Element of Seg d holds [(l . i),(r . i)] is Gap of G . i ) & ( for i being Element of Seg d holds l . i < r . i or for i being Element of Seg d holds r . i < l . i ) ) )