Notation of a pregallery

I'm transcribing parts of Harm van der Lek's thesis 'The homotopy type of complex hyperplane complements' and due to it being written in 1983 the typesetting isn't very detailed. In latex, how should the picture ** be written (just the part that comes after 'This pregallery is denoted:')? Are the $S_i$'s and $K_i$'s supposed to be the same size, or was that done due to printing constraints?

Edit: If we take them to be the same size then what is the correct way of recreating this in latex, and for those with the knowledge, how about MathML? Note that for MathML my attempt is this:

<msup>
<msub><mi>S</mi><mn>0</mn></msub>
<mstyle scriptlevel="0"><msub><mi>K</mi><mn>1</mn></msub></mstyle>
</msup>

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It seems to me that the $K$'s and $S$'s should be the same size. They play the same role as the edges and vertices in a path in a graph. The reason they are written on different levels is just to make the alternating structure easier to see. In particular, the K's are not exponents, not are the S's subscripts.

In LaTeX, I'd code this as a two-row matrix in which half of the entries are blank.

Second Edit: I just got the following email confirming what I had written above:

Dear Professor Blass,

I just saw your comment on Math Overflow on a question regarding the thesis of Harm van der Lek. Van der Lek wrote his thesis under my guidance and I can affirm that your answer is essentially correct. I am not a registered user of Math Overflow (and I have no way to find out who Callister is or what his email address is) and so perhaps you can forward to him his message (or add it as a comment).

With kind regards, Eduard Looijenga

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Wasn't expecting an answer from his supervisor. Thanks. –  Calliston May 4 '13 at 6:19