Основы теории английского языка. Листунова Е.И. - 58 стр.

              Repetition of to before Several Infinitives

      1. When there are several infinitives with the same or similar
function to is put only before the first infinitive. But if emphasis or
contrast is intended, to is repeated before each infinitive:
      ...It was his delight to run into the garden after a shower of rain
and shake the rose bush over him (Mansfield). To be or not to be —
that is the question (Shakespeare).
      2. In colloquial speech the particle to is often used without the
infinitive if the latter is clearly understood from the preceding context.
This construction is used with verbs expressing actions:
      «You can laugh if you want to,» she said. «I know it’s comic»
(Snîw). «You must come and have dinner with me.» — «Thank you,
uncle Jol yon, I should like to!» (Galsworthy). Jago has sacrificed
himself for the college, just as every college officer has to (Snow).

                             Split Infinitive

      The particle to is sometimes separated from the infinitive by
an adverb or an emphatic particle; the construction is called a
«Split Infinitive»:
      They were seen to just touch each other’s hands (Galsworthy).
...She seemed to really like her grey old bonnet better... (Leacock). It
had been impossible to seriously confide to June his conviction...
(Galsworthy). He was unable, however, to long keep silence (Galswor-
thy). The working masses of Russia were the first to decisively storm
capitalism, the first to take the path to Socialism.
      Sometimes this separation of to from the infinitive is necessary
to avoid ambiguity. If in the sentence They were unwilling to wholly
manufacture new goods — wholly is put in front of the to, it tends to
adhere to unwilling; if it is placed after manufacture, it attaches itself
to new, and the meaning is changed.

             The Subjective and the Objective Infinitive

      The action expressed by the infinitive may refer either to the
subject or to the object of the sentence.
      When the action expressed by the infinitive refers to the subject
of the sentence, the infinitive is a subjective infinitive:


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