View source for Exercises:Mond - Topology - 2/Section B/Question 6/Picture

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| <center><span style="font-size:1.2em;"><m>\xymatrix{
 \bullet \ar@{<-}[dd]_B \ar@{<.}@/^1em/[rrr]^{(A)} \ar@{<-}[r]_{A_1} & \bullet \ar@{<-}[r]_{A_2} \ar@{}[ddr]|(.5){\mathbf{M} } \ar@{-->}@/_.65em/[dd]^{C_1} \ar@{-->}@/^.65em/[dd] & \bullet \ar@{<-}[r]_{A_3} \ar@{-->}@/_.65em/[dd]^{C_2} \ar@{-->}@/^.65em/[dd] &  \bullet \\
 & & &\\
 \bullet \ar@{.>}@/_1em/[rrr]_{(A)} \ar[r]^{A_3} & \bullet \ar[r]^{A_2} & \bullet \ar[r]^{A_1} &  \bullet \ar@{<-}[uu]_B
}</m></span></center><br/>
We take {{M|\mathbb{RP}^2}} (represented here as the gluings {{M|A}} and {{M|B}}) and cut it (creating gluings {{M|C_1}} and {{M|C_2}}), thus diving {{M|A}} into {{M|A_1}}, {{M|A_2}} and {{M|A_3}}. The central strip is called {{M|M}}
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! {{M|M}} is a Mobius strip inside {{M|\mathbb{RP}^2}}
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